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	$178.32	11.679%	$199.146	$199.15	$199.15	$199.10
Purchase #2	$65.30	10.107%	$71.8999	$71.90	$71.90	$71.90
Purchase #3	$200.28	12.171%	$224.6561	$224.66	$224.65	$224.70
Purchase #4	$176.44	5.660%	$186.4265	$186.43	$186.45	$186.40
Purchase #5	$229.79	10.316%	$253.4951	$253.50	$253.50	$253.50
Purchase #6	$152.87	10.456%	$168.8541	$168.85	$168.85	$168.90
Purchase #7	$123.45	13.449%	$140.0528	$140.05	$140.05	$140.10
7 purchase totals =	$1,126.45		$1,244.5305	$1,244.54	$1,244.55	$1,244.60