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	$110.94	8.131%	$119.9605	$119.96	$119.95	$120.00
Purchase #2	$82.39	8.126%	$89.085	$89.09	$89.10	$89.10
Purchase #3	$142.60	6.671%	$152.1128	$152.11	$152.10	$152.10
Purchase #4	$68.25	5.361%	$71.9089	$71.91	$71.90	$71.90
Purchase #5	$90.76	7.293%	$97.3791	$97.38	$97.40	$97.40
Purchase #6	$199.92	13.805%	$227.519	$227.52	$227.50	$227.50
Purchase #7	$151.56	8.286%	$164.1183	$164.12	$164.10	$164.10
7 purchase totals =	$846.42		$922.0836	$922.09	$922.05	$922.10