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	$53.75	9.814%	$59.025	$59.03	$59.05	$59.00
Purchase #2	$220.77	10.117%	$243.1053	$243.11	$243.10	$243.10
Purchase #3	$48.54	5.527%	$51.2228	$51.22	$51.20	$51.20
Purchase #4	$160.48	7.565%	$172.6203	$172.62	$172.60	$172.60
Purchase #5	$86.81	10.336%	$95.7827	$95.78	$95.80	$95.80
Purchase #6	$104.25	13.260%	$118.0736	$118.07	$118.05	$118.10
Purchase #7	$6.91	13.176%	$7.8205	$7.82	$7.80	$7.80
7 purchase totals =	$681.51		$747.6502	$747.65	$747.60	$747.60