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	$61.82	8.607%	$67.1408	$67.14	$67.15	$67.10
Purchase #2	$211.76	13.531%	$240.4132	$240.41	$240.40	$240.40
Purchase #3	$55.53	6.829%	$59.3221	$59.32	$59.30	$59.30
Purchase #4	$66.68	7.528%	$71.6997	$71.70	$71.70	$71.70
Purchase #5	$204.38	10.546%	$225.9339	$225.93	$225.95	$225.90
Purchase #6	$182.74	12.844%	$206.2111	$206.21	$206.20	$206.20
Purchase #7	$105.81	4.704%	$110.7873	$110.79	$110.80	$110.80
7 purchase totals =	$888.72		$981.5081	$981.50	$981.50	$981.40