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	$152.92	3.270%	$157.9205	$157.92	$157.90	$157.90
Purchase #2	$106.33	12.275%	$119.382	$119.38	$119.40	$119.40
Purchase #3	$133.87	12.470%	$150.5636	$150.56	$150.55	$150.60
Purchase #4	$212.98	4.811%	$223.2265	$223.23	$223.25	$223.20
Purchase #5	$132.81	13.594%	$150.8642	$150.86	$150.85	$150.90
Purchase #6	$204.51	10.288%	$225.55	$225.55	$225.55	$225.60
Purchase #7	$25.58	7.162%	$27.412	$27.41	$27.40	$27.40
7 purchase totals =	$969.00		$1,054.9188	$1,054.91	$1,054.90	$1,055.00