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	$243.84	8.485%	$264.5298	$264.53	$264.55	$264.50
Purchase #2	$213.92	3.424%	$221.2446	$221.24	$221.25	$221.20
Purchase #3	$109.78	13.194%	$124.2644	$124.26	$124.25	$124.30
Purchase #4	$206.27	7.874%	$222.5117	$222.51	$222.50	$222.50
Purchase #5	$92.36	7.594%	$99.3738	$99.37	$99.35	$99.40
Purchase #6	$157.99	6.867%	$168.8392	$168.84	$168.85	$168.80
Purchase #7	$132.43	11.403%	$147.531	$147.53	$147.55	$147.50
7 purchase totals =	$1,156.59		$1,248.2945	$1,248.28	$1,248.30	$1,248.20