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	$128.75	9.618%	$141.1332	$141.13	$141.15	$141.10
Purchase #2	$244.25	10.499%	$269.8938	$269.89	$269.90	$269.90
Purchase #3	$130.30	12.672%	$146.8116	$146.81	$146.80	$146.80
Purchase #4	$250.79	11.825%	$280.4459	$280.45	$280.45	$280.40
Purchase #5	$72.88	6.859%	$77.8788	$77.88	$77.90	$77.90
Purchase #6	$197.54	5.514%	$208.4324	$208.43	$208.45	$208.40
Purchase #7	$223.26	12.628%	$251.4533	$251.45	$251.45	$251.50
7 purchase totals =	$1,247.77		$1,376.0490	$1,376.04	$1,376.10	$1,376.00