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	$142.82	10.463%	$157.7633	$157.76	$157.75	$157.80
Purchase #2	$182.67	3.397%	$188.8753	$188.88	$188.90	$188.90
Purchase #3	$137.33	9.847%	$150.8529	$150.85	$150.85	$150.90
Purchase #4	$53.86	8.111%	$58.2286	$58.23	$58.25	$58.20
Purchase #5	$198.54	11.843%	$222.0531	$222.05	$222.05	$222.10
Purchase #6	$175.53	9.344%	$191.9315	$191.93	$191.95	$191.90
Purchase #7	$30.73	6.413%	$32.7007	$32.70	$32.70	$32.70
7 purchase totals =	$921.48		$1,002.4054	$1,002.40	$1,002.45	$1,002.50