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	$64.93	10.665%	$71.8548	$71.85	$71.85	$71.90
Purchase #2	$113.41	4.714%	$118.7561	$118.76	$118.75	$118.80
Purchase #3	$72.29	6.784%	$77.1942	$77.19	$77.20	$77.20
Purchase #4	$40.93	4.787%	$42.8893	$42.89	$42.90	$42.90
Purchase #5	$94.32	13.600%	$107.1475	$107.15	$107.15	$107.10
Purchase #6	$184.72	6.409%	$196.5587	$196.56	$196.55	$196.60
Purchase #7	$86.92	7.363%	$93.3199	$93.32	$93.30	$93.30
7 purchase totals =	$657.52		$707.7205	$707.72	$707.70	$707.80