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	$226.88	11.799%	$253.6496	$253.65	$253.65	$253.60
Purchase #2	$89.38	7.304%	$95.9083	$95.91	$95.90	$95.90
Purchase #3	$6.88	11.161%	$7.6479	$7.65	$7.65	$7.60
Purchase #4	$165.83	6.357%	$176.3718	$176.37	$176.35	$176.40
Purchase #5	$217.67	6.800%	$232.4716	$232.47	$232.45	$232.50
Purchase #6	$86.55	3.422%	$89.5117	$89.51	$89.50	$89.50
Purchase #7	$78.48	3.390%	$81.1405	$81.14	$81.15	$81.10
7 purchase totals =	$871.67		$936.7014	$936.70	$936.65	$936.60