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	$223.46	13.195%	$252.9455	$252.95	$252.95	$252.90
Purchase #2	$20.97	4.201%	$21.8509	$21.85	$21.85	$21.90
Purchase #3	$104.66	9.582%	$114.6885	$114.69	$114.70	$114.70
Purchase #4	$139.98	7.605%	$150.6255	$150.63	$150.65	$150.60
Purchase #5	$170.41	12.585%	$191.8561	$191.86	$191.85	$191.90
Purchase #6	$67.71	6.814%	$72.3238	$72.32	$72.30	$72.30
Purchase #7	$83.98	7.318%	$90.1257	$90.13	$90.15	$90.10
7 purchase totals =	$811.17		$894.4160	$894.43	$894.45	$894.40