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	$104.82	11.312%	$116.6772	$116.68	$116.70	$116.70
Purchase #2	$64.37	13.566%	$73.1024	$73.10	$73.10	$73.10
Purchase #3	$125.29	12.200%	$140.5754	$140.58	$140.60	$140.60
Purchase #4	$146.89	13.300%	$166.4264	$166.43	$166.45	$166.40
Purchase #5	$29.71	12.798%	$33.5123	$33.51	$33.50	$33.50
Purchase #6	$229.91	6.419%	$244.6679	$244.67	$244.65	$244.70
Purchase #7	$156.90	7.217%	$168.2235	$168.22	$168.20	$168.20
7 purchase totals =	$857.89		$943.1851	$943.19	$943.20	$943.20