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	$213.73	4.401%	$223.1363	$223.14	$223.15	$223.10
Purchase #2	$134.45	5.165%	$141.3943	$141.39	$141.40	$141.40
Purchase #3	$145.51	11.629%	$162.4314	$162.43	$162.45	$162.40
Purchase #4	$85.95	3.849%	$89.2582	$89.26	$89.25	$89.30
Purchase #5	$54.78	11.593%	$61.1306	$61.13	$61.15	$61.10
Purchase #6	$7.36	11.420%	$8.2005	$8.20	$8.20	$8.20
Purchase #7	$249.33	9.240%	$272.3681	$272.37	$272.35	$272.40
7 purchase totals =	$891.11		$957.9194	$957.92	$957.95	$957.90