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	$168.91	9.637%	$185.1879	$185.19	$185.20	$185.20
Purchase #2	$46.92	4.132%	$48.8587	$48.86	$48.85	$48.90
Purchase #3	$92.68	4.846%	$97.1713	$97.17	$97.15	$97.20
Purchase #4	$18.26	10.470%	$20.1718	$20.17	$20.15	$20.20
Purchase #5	$50.82	5.814%	$53.7747	$53.77	$53.75	$53.80
Purchase #6	$199.42	11.567%	$222.4869	$222.49	$222.50	$222.50
Purchase #7	$165.95	10.136%	$182.7707	$182.77	$182.75	$182.80
7 purchase totals =	$742.96		$810.4220	$810.42	$810.35	$810.60