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	$89.98	7.495%	$96.724	$96.72	$96.70	$96.70
Purchase #2	$151.37	13.732%	$172.1561	$172.16	$172.15	$172.20
Purchase #3	$195.95	13.562%	$222.5247	$222.52	$222.50	$222.50
Purchase #4	$241.70	8.130%	$261.3502	$261.35	$261.35	$261.40
Purchase #5	$149.28	8.833%	$162.4659	$162.47	$162.45	$162.50
Purchase #6	$21.72	5.438%	$22.9011	$22.90	$22.90	$22.90
Purchase #7	$91.52	9.352%	$100.079	$100.08	$100.10	$100.10
7 purchase totals =	$941.52		$1,038.2010	$1,038.20	$1,038.15	$1,038.30