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	$168.91	12.620%	$190.2264	$190.23	$190.25	$190.20
Purchase #2	$144.37	8.706%	$156.9389	$156.94	$156.95	$156.90
Purchase #3	$131.55	5.187%	$138.3735	$138.37	$138.35	$138.40
Purchase #4	$84.69	5.245%	$89.132	$89.13	$89.15	$89.10
Purchase #5	$223.48	5.325%	$235.3803	$235.38	$235.40	$235.40
Purchase #6	$21.46	10.679%	$23.7517	$23.75	$23.75	$23.80
Purchase #7	$99.55	11.616%	$111.1137	$111.11	$111.10	$111.10
7 purchase totals =	$874.01		$944.9165	$944.91	$944.95	$944.90