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	$96.41	7.210%	$103.3612	$103.36	$103.35	$103.40
Purchase #2	$165.33	4.547%	$172.8476	$172.85	$172.85	$172.80
Purchase #3	$86.95	10.587%	$96.1554	$96.16	$96.15	$96.20
Purchase #4	$19.62	3.734%	$20.3526	$20.35	$20.35	$20.40
Purchase #5	$30.57	5.284%	$32.1853	$32.19	$32.20	$32.20
Purchase #6	$158.95	3.491%	$164.4989	$164.50	$164.50	$164.50
Purchase #7	$38.37	7.860%	$41.3859	$41.39	$41.40	$41.40
7 purchase totals =	$596.20		$630.7869	$630.80	$630.80	$630.90