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	$221.62	4.262%	$231.0654	$231.07	$231.05	$231.10
Purchase #2	$118.51	4.567%	$123.9224	$123.92	$123.90	$123.90
Purchase #3	$100.63	9.167%	$109.8548	$109.85	$109.85	$109.90
Purchase #4	$150.75	4.362%	$157.3257	$157.33	$157.35	$157.30
Purchase #5	$134.65	6.869%	$143.8991	$143.90	$143.90	$143.90
Purchase #6	$240.66	12.396%	$270.4922	$270.49	$270.50	$270.50
Purchase #7	$6.91	10.500%	$7.6356	$7.64	$7.65	$7.60
7 purchase totals =	$973.73		$1,044.1952	$1,044.20	$1,044.20	$1,044.20