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	$223.36	13.614%	$253.7682	$253.77	$253.75	$253.80
Purchase #2	$47.71	12.120%	$53.4925	$53.49	$53.50	$53.50
Purchase #3	$81.42	11.366%	$90.6742	$90.67	$90.65	$90.70
Purchase #4	$86.51	4.196%	$90.14	$90.14	$90.15	$90.10
Purchase #5	$8.80	8.499%	$9.5479	$9.55	$9.55	$9.50
Purchase #6	$52.87	10.481%	$58.4113	$58.41	$58.40	$58.40
Purchase #7	$171.47	9.725%	$188.1455	$188.15	$188.15	$188.10
7 purchase totals =	$672.14		$744.1796	$744.18	$744.15	$744.10