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	$246.59	9.140%	$269.1283	$269.13	$269.15	$269.10
Purchase #2	$9.98	5.735%	$10.5524	$10.55	$10.55	$10.60
Purchase #3	$159.26	3.777%	$165.2753	$165.28	$165.30	$165.30
Purchase #4	$33.37	13.344%	$37.8229	$37.82	$37.80	$37.80
Purchase #5	$238.91	12.370%	$268.4632	$268.46	$268.45	$268.50
Purchase #6	$45.88	9.577%	$50.2739	$50.27	$50.25	$50.30
Purchase #7	$227.96	11.760%	$254.7681	$254.77	$254.75	$254.80
7 purchase totals =	$961.95		$1,056.2841	$1,056.28	$1,056.25	$1,056.40