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	$48.98	11.444%	$54.5853	$54.59	$54.60	$54.60
Purchase #2	$125.89	3.486%	$130.2785	$130.28	$130.30	$130.30
Purchase #3	$6.42	3.532%	$6.6468	$6.65	$6.65	$6.60
Purchase #4	$235.31	3.222%	$242.8917	$242.89	$242.90	$242.90
Purchase #5	$20.59	8.801%	$22.4021	$22.40	$22.40	$22.40
Purchase #6	$6.78	8.513%	$7.3572	$7.36	$7.35	$7.40
Purchase #7	$121.61	12.831%	$137.2138	$137.21	$137.20	$137.20
7 purchase totals =	$565.58		$601.3754	$601.38	$601.40	$601.40