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	$72.54	13.196%	$82.1124	$82.11	$82.10	$82.10
Purchase #2	$175.72	11.592%	$196.0895	$196.09	$196.10	$196.10
Purchase #3	$66.81	8.679%	$72.6084	$72.61	$72.60	$72.60
Purchase #4	$93.75	3.793%	$97.3059	$97.31	$97.30	$97.30
Purchase #5	$64.90	11.867%	$72.6017	$72.60	$72.60	$72.60
Purchase #6	$96.73	9.775%	$106.1854	$106.19	$106.20	$106.20
Purchase #7	$233.56	8.217%	$252.7516	$252.75	$252.75	$252.80
7 purchase totals =	$804.01		$879.6549	$879.66	$879.65	$879.70