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	$39.74	9.749%	$43.6143	$43.61	$43.60	$43.60
Purchase #2	$120.34	7.406%	$129.2524	$129.25	$129.25	$129.30
Purchase #3	$205.89	8.298%	$222.9748	$222.97	$222.95	$223.00
Purchase #4	$152.88	8.375%	$165.6837	$165.68	$165.70	$165.70
Purchase #5	$84.54	5.505%	$89.1939	$89.19	$89.20	$89.20
Purchase #6	$135.52	10.750%	$150.0884	$150.09	$150.10	$150.10
Purchase #7	$204.65	5.473%	$215.8505	$215.85	$215.85	$215.90
7 purchase totals =	$943.56		$1,016.6580	$1,016.64	$1,016.65	$1,016.80