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	$199.58	7.355%	$214.2591	$214.26	$214.25	$214.30
Purchase #2	$72.69	5.303%	$76.5448	$76.54	$76.55	$76.50
Purchase #3	$131.68	8.712%	$143.152	$143.15	$143.15	$143.20
Purchase #4	$99.80	12.455%	$112.2301	$112.23	$112.25	$112.20
Purchase #5	$99.41	5.772%	$105.1479	$105.15	$105.15	$105.10
Purchase #6	$216.94	12.734%	$244.5651	$244.57	$244.55	$244.60
Purchase #7	$91.50	10.814%	$101.3948	$101.39	$101.40	$101.40
7 purchase totals =	$911.60		$997.2938	$997.29	$997.30	$997.30