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	$9.62	5.413%	$10.1407	$10.14	$10.15	$10.10
Purchase #2	$198.88	6.610%	$212.026	$212.03	$212.05	$212.00
Purchase #3	$65.39	10.503%	$72.2579	$72.26	$72.25	$72.30
Purchase #4	$122.38	7.378%	$131.4092	$131.41	$131.40	$131.40
Purchase #5	$242.56	6.559%	$258.4695	$258.47	$258.45	$258.50
Purchase #6	$167.77	11.180%	$186.5267	$186.53	$186.55	$186.50
Purchase #7	$246.75	13.259%	$279.4666	$279.47	$279.45	$279.50
7 purchase totals =	$1,053.35		$1,150.2966	$1,150.31	$1,150.30	$1,150.30