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	$235.46	11.586%	$262.7404	$262.74	$262.75	$262.70
Purchase #2	$27.63	4.553%	$28.888	$28.89	$28.90	$28.90
Purchase #3	$10.87	13.735%	$12.363	$12.36	$12.35	$12.40
Purchase #4	$75.50	10.579%	$83.4871	$83.49	$83.50	$83.50
Purchase #5	$211.67	12.826%	$238.8188	$238.82	$238.80	$238.80
Purchase #6	$218.35	12.273%	$245.1481	$245.15	$245.15	$245.10
Purchase #7	$46.95	12.558%	$52.846	$52.85	$52.85	$52.80
7 purchase totals =	$826.43		$924.2914	$924.30	$924.30	$924.20