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	$147.25	7.506%	$158.3026	$158.30	$158.30	$158.30
Purchase #2	$232.72	13.584%	$264.3327	$264.33	$264.35	$264.30
Purchase #3	$30.96	6.530%	$32.9817	$32.98	$33.00	$33.00
Purchase #4	$70.65	10.579%	$78.1241	$78.12	$78.10	$78.10
Purchase #5	$22.50	13.507%	$25.5391	$25.54	$25.55	$25.50
Purchase #6	$39.41	9.283%	$43.0684	$43.07	$43.05	$43.10
Purchase #7	$241.56	11.541%	$269.4384	$269.44	$269.45	$269.40
7 purchase totals =	$785.05		$871.7870	$871.78	$871.80	$871.70