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	$186.54	12.142%	$209.1897	$209.19	$209.20	$209.20
Purchase #2	$53.28	12.289%	$59.8276	$59.83	$59.85	$59.80
Purchase #3	$158.51	10.734%	$175.5245	$175.52	$175.50	$175.50
Purchase #4	$228.93	4.315%	$238.8083	$238.81	$238.80	$238.80
Purchase #5	$229.95	12.340%	$258.3258	$258.33	$258.35	$258.30
Purchase #6	$74.28	4.623%	$77.714	$77.71	$77.70	$77.70
Purchase #7	$79.91	7.295%	$85.7394	$85.74	$85.75	$85.70
7 purchase totals =	$1,011.40		$1,105.1293	$1,105.13	$1,105.15	$1,105.00