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	$142.73	11.547%	$159.211	$159.21	$159.20	$159.20
Purchase #2	$233.32	6.354%	$248.1452	$248.15	$248.15	$248.10
Purchase #3	$233.48	12.515%	$262.7	$262.70	$262.70	$262.70
Purchase #4	$190.50	4.689%	$199.4325	$199.43	$199.45	$199.40
Purchase #5	$40.32	12.523%	$45.3693	$45.37	$45.35	$45.40
Purchase #6	$148.82	7.383%	$159.8074	$159.81	$159.80	$159.80
Purchase #7	$92.46	7.434%	$99.3335	$99.33	$99.35	$99.30
7 purchase totals =	$1,081.63		$1,173.9989	$1,174.00	$1,174.00	$1,173.90