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	$168.37	8.316%	$182.3716	$182.37	$182.35	$182.40
Purchase #2	$25.72	12.371%	$28.9018	$28.90	$28.90	$28.90
Purchase #3	$6.94	5.645%	$7.3318	$7.33	$7.35	$7.30
Purchase #4	$149.60	12.619%	$168.478	$168.48	$168.50	$168.50
Purchase #5	$129.59	10.639%	$143.3771	$143.38	$143.40	$143.40
Purchase #6	$48.29	12.459%	$54.3065	$54.31	$54.30	$54.30
Purchase #7	$46.66	7.651%	$50.23	$50.23	$50.25	$50.20
7 purchase totals =	$575.17		$634.9968	$635.00	$635.05	$635.00