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	$203.60	9.658%	$223.2637	$223.26	$223.25	$223.30
Purchase #2	$226.72	9.499%	$248.2561	$248.26	$248.25	$248.30
Purchase #3	$106.41	9.336%	$116.3444	$116.34	$116.35	$116.30
Purchase #4	$141.34	10.111%	$155.6309	$155.63	$155.65	$155.60
Purchase #5	$140.52	10.316%	$155.016	$155.02	$155.00	$155.00
Purchase #6	$154.66	8.731%	$168.1634	$168.16	$168.15	$168.20
Purchase #7	$34.49	7.572%	$37.1016	$37.10	$37.10	$37.10
7 purchase totals =	$1,007.74		$1,103.7761	$1,103.77	$1,103.75	$1,103.80