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	$151.26	11.141%	$168.1119	$168.11	$168.10	$168.10
Purchase #2	$139.79	11.129%	$155.3472	$155.35	$155.35	$155.30
Purchase #3	$111.94	7.393%	$120.2157	$120.22	$120.20	$120.20
Purchase #4	$236.84	11.572%	$264.2471	$264.25	$264.25	$264.20
Purchase #5	$41.85	10.174%	$46.1078	$46.11	$46.10	$46.10
Purchase #6	$249.69	5.522%	$263.4779	$263.48	$263.50	$263.50
Purchase #7	$60.85	7.431%	$65.3718	$65.37	$65.35	$65.40
7 purchase totals =	$992.22		$1,082.8794	$1,082.89	$1,082.85	$1,082.80