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	$67.33	7.760%	$72.5548	$72.55	$72.55	$72.60
Purchase #2	$24.95	5.501%	$26.3225	$26.32	$26.30	$26.30
Purchase #3	$22.50	11.644%	$25.1199	$25.12	$25.10	$25.10
Purchase #4	$128.54	12.388%	$144.4635	$144.46	$144.45	$144.50
Purchase #5	$248.98	12.778%	$280.7947	$280.79	$280.80	$280.80
Purchase #6	$80.95	10.556%	$89.4951	$89.50	$89.50	$89.50
Purchase #7	$246.84	3.847%	$256.3359	$256.34	$256.35	$256.30
7 purchase totals =	$820.09		$895.0864	$895.08	$895.05	$895.10