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	$53.54	13.757%	$60.9055	$60.91	$60.90	$60.90
Purchase #2	$78.67	13.716%	$89.4604	$89.46	$89.45	$89.50
Purchase #3	$103.53	12.374%	$116.3408	$116.34	$116.35	$116.30
Purchase #4	$48.50	12.793%	$54.7046	$54.70	$54.70	$54.70
Purchase #5	$86.28	9.610%	$94.5715	$94.57	$94.55	$94.60
Purchase #6	$188.85	10.748%	$209.1476	$209.15	$209.15	$209.10
Purchase #7	$158.28	13.361%	$179.4278	$179.43	$179.45	$179.40
7 purchase totals =	$717.65		$804.5582	$804.56	$804.55	$804.50