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	$168.37	11.472%	$187.6854	$187.69	$187.70	$187.70
Purchase #2	$120.86	10.377%	$133.4016	$133.40	$133.40	$133.40
Purchase #3	$213.54	12.422%	$240.0659	$240.07	$240.05	$240.10
Purchase #4	$178.37	12.464%	$200.602	$200.60	$200.60	$200.60
Purchase #5	$95.76	3.817%	$99.4152	$99.42	$99.40	$99.40
Purchase #6	$117.88	6.584%	$125.6412	$125.64	$125.65	$125.60
Purchase #7	$101.75	12.179%	$114.1421	$114.14	$114.15	$114.10
7 purchase totals =	$996.53		$1,100.9534	$1,100.96	$1,100.95	$1,100.90