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	$200.48	5.456%	$211.4182	$211.42	$211.40	$211.40
Purchase #2	$212.59	13.520%	$241.3322	$241.33	$241.35	$241.30
Purchase #3	$95.77	10.221%	$105.5587	$105.56	$105.55	$105.60
Purchase #4	$206.37	3.763%	$214.1357	$214.14	$214.15	$214.10
Purchase #5	$155.58	6.221%	$165.2586	$165.26	$165.25	$165.30
Purchase #6	$29.97	10.638%	$33.1582	$33.16	$33.15	$33.20
Purchase #7	$243.31	5.568%	$256.8575	$256.86	$256.85	$256.90
7 purchase totals =	$1,144.07		$1,227.7191	$1,227.73	$1,227.70	$1,227.80