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	$172.85	7.415%	$185.6668	$185.67	$185.65	$185.70
Purchase #2	$35.36	8.130%	$38.2348	$38.23	$38.25	$38.20
Purchase #3	$88.55	13.336%	$100.359	$100.36	$100.35	$100.40
Purchase #4	$37.79	10.702%	$41.8343	$41.83	$41.85	$41.80
Purchase #5	$30.51	7.181%	$32.7009	$32.70	$32.70	$32.70
Purchase #6	$41.54	6.295%	$44.1549	$44.15	$44.15	$44.20
Purchase #7	$82.52	11.742%	$92.2095	$92.21	$92.20	$92.20
7 purchase totals =	$489.12		$535.1602	$535.15	$535.15	$535.20