Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.69	3.807%	$227.0155	$227.02	$227.00	$227.00
Purchase #2	$154.59	11.178%	$171.8701	$171.87	$171.85	$171.90
Purchase #3	$112.87	12.840%	$127.3625	$127.36	$127.35	$127.40
Purchase #4	$233.96	3.443%	$242.0152	$242.02	$242.00	$242.00
Purchase #5	$200.58	11.232%	$223.1091	$223.11	$223.10	$223.10
Purchase #6	$124.32	10.542%	$137.4258	$137.43	$137.45	$137.40
Purchase #7	$169.43	11.644%	$189.1584	$189.16	$189.15	$189.20
7 purchase totals =	$1,214.44		$1,317.9566	$1,317.97	$1,317.90	$1,318.00