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	$60.86	11.701%	$67.9812	$67.98	$68.00	$68.00
Purchase #2	$118.96	5.700%	$125.7407	$125.74	$125.75	$125.70
Purchase #3	$91.82	10.232%	$101.215	$101.22	$101.20	$101.20
Purchase #4	$53.52	10.443%	$59.1091	$59.11	$59.10	$59.10
Purchase #5	$210.80	10.862%	$233.6971	$233.70	$233.70	$233.70
Purchase #6	$37.77	4.844%	$39.5996	$39.60	$39.60	$39.60
Purchase #7	$167.66	10.482%	$185.2341	$185.23	$185.25	$185.20
7 purchase totals =	$741.39		$812.5768	$812.58	$812.60	$812.50