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	$118.61	10.298%	$130.8245	$130.82	$130.80	$130.80
Purchase #2	$134.47	11.672%	$150.1653	$150.17	$150.15	$150.20
Purchase #3	$123.72	9.138%	$135.0255	$135.03	$135.05	$135.00
Purchase #4	$86.28	9.596%	$94.5594	$94.56	$94.55	$94.60
Purchase #5	$91.72	5.599%	$96.8554	$96.86	$96.85	$96.90
Purchase #6	$119.37	5.647%	$126.1108	$126.11	$126.10	$126.10
Purchase #7	$81.52	9.730%	$89.4519	$89.45	$89.45	$89.50
7 purchase totals =	$755.69		$822.9928	$823.00	$822.95	$823.10