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	$184.70	8.584%	$200.5546	$200.55	$200.55	$200.60
Purchase #2	$26.43	7.436%	$28.3953	$28.40	$28.40	$28.40
Purchase #3	$98.78	12.490%	$111.1176	$111.12	$111.10	$111.10
Purchase #4	$202.37	10.741%	$224.1066	$224.11	$224.10	$224.10
Purchase #5	$136.29	3.106%	$140.5232	$140.52	$140.50	$140.50
Purchase #6	$85.83	4.167%	$89.4065	$89.41	$89.40	$89.40
Purchase #7	$75.33	10.719%	$83.4046	$83.40	$83.40	$83.40
7 purchase totals =	$809.73		$877.5084	$877.51	$877.45	$877.50