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	$32.75	10.269%	$36.1131	$36.11	$36.10	$36.10
Purchase #2	$208.62	3.321%	$215.5483	$215.55	$215.55	$215.50
Purchase #3	$174.83	12.329%	$196.3848	$196.38	$196.40	$196.40
Purchase #4	$245.80	10.644%	$271.963	$271.96	$271.95	$272.00
Purchase #5	$152.97	6.145%	$162.37	$162.37	$162.35	$162.40
Purchase #6	$231.35	4.749%	$242.3368	$242.34	$242.35	$242.30
Purchase #7	$151.61	13.536%	$172.1319	$172.13	$172.15	$172.10
7 purchase totals =	$1,197.93		$1,296.8479	$1,296.84	$1,296.85	$1,296.80