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	$75.70	13.198%	$85.6909	$85.69	$85.70	$85.70
Purchase #2	$162.69	10.739%	$180.1613	$180.16	$180.15	$180.20
Purchase #3	$118.46	10.740%	$131.1826	$131.18	$131.20	$131.20
Purchase #4	$219.68	12.753%	$247.6958	$247.70	$247.70	$247.70
Purchase #5	$149.34	3.453%	$154.4967	$154.50	$154.50	$154.50
Purchase #6	$155.44	4.558%	$162.525	$162.53	$162.55	$162.50
Purchase #7	$92.77	7.582%	$99.8038	$99.80	$99.80	$99.80
7 purchase totals =	$974.08		$1,061.5561	$1,061.56	$1,061.60	$1,061.60