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	$191.78	11.489%	$213.8136	$213.81	$213.80	$213.80
Purchase #2	$10.73	13.748%	$12.2052	$12.21	$12.20	$12.20
Purchase #3	$85.51	8.431%	$92.7193	$92.72	$92.70	$92.70
Purchase #4	$76.52	7.279%	$82.0899	$82.09	$82.10	$82.10
Purchase #5	$78.77	13.501%	$89.4047	$89.40	$89.40	$89.40
Purchase #6	$41.30	10.753%	$45.741	$45.74	$45.75	$45.70
Purchase #7	$148.78	13.406%	$168.7254	$168.73	$168.75	$168.70
7 purchase totals =	$633.39		$704.6991	$704.70	$704.70	$704.60