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	$65.27	3.269%	$67.4037	$67.40	$67.40	$67.40
Purchase #2	$70.25	9.551%	$76.9596	$76.96	$76.95	$77.00
Purchase #3	$80.38	6.348%	$85.4825	$85.48	$85.50	$85.50
Purchase #4	$107.72	8.351%	$116.7157	$116.72	$116.70	$116.70
Purchase #5	$155.29	3.364%	$160.514	$160.51	$160.50	$160.50
Purchase #6	$243.46	7.579%	$261.9118	$261.91	$261.90	$261.90
Purchase #7	$200.27	12.408%	$225.1195	$225.12	$225.10	$225.10
7 purchase totals =	$922.64		$994.1068	$994.10	$994.05	$994.10