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	$172.48	7.734%	$185.8196	$185.82	$185.80	$185.80
Purchase #2	$38.40	11.420%	$42.7853	$42.79	$42.80	$42.80
Purchase #3	$6.86	8.363%	$7.4337	$7.43	$7.45	$7.40
Purchase #4	$18.36	4.707%	$19.2242	$19.22	$19.20	$19.20
Purchase #5	$52.68	6.756%	$56.2391	$56.24	$56.25	$56.20
Purchase #6	$81.92	13.279%	$92.7982	$92.80	$92.80	$92.80
Purchase #7	$209.69	6.448%	$223.2108	$223.21	$223.20	$223.20
7 purchase totals =	$580.39		$627.5109	$627.51	$627.50	$627.40