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	$245.29	7.703%	$264.1847	$264.18	$264.20	$264.20
Purchase #2	$99.57	6.363%	$105.9056	$105.91	$105.90	$105.90
Purchase #3	$166.79	13.628%	$189.5201	$189.52	$189.50	$189.50
Purchase #4	$87.82	10.630%	$97.1553	$97.16	$97.15	$97.20
Purchase #5	$167.41	4.560%	$175.0439	$175.04	$175.05	$175.00
Purchase #6	$64.72	10.782%	$71.6981	$71.70	$71.70	$71.70
Purchase #7	$141.83	11.691%	$158.4113	$158.41	$158.40	$158.40
7 purchase totals =	$973.43		$1,061.9190	$1,061.92	$1,061.90	$1,061.90