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	$43.89	13.398%	$49.7704	$49.77	$49.75	$49.80
Purchase #2	$225.58	12.279%	$253.279	$253.28	$253.30	$253.30
Purchase #3	$188.45	11.222%	$209.5979	$209.60	$209.60	$209.60
Purchase #4	$59.83	11.736%	$66.8516	$66.85	$66.85	$66.90
Purchase #5	$180.37	9.502%	$197.5088	$197.51	$197.50	$197.50
Purchase #6	$59.63	6.846%	$63.7123	$63.71	$63.70	$63.70
Purchase #7	$155.29	13.369%	$176.0507	$176.05	$176.05	$176.10
7 purchase totals =	$913.04		$1,016.7707	$1,016.77	$1,016.75	$1,016.90