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	$48.38	10.198%	$53.3138	$53.31	$53.30	$53.30
Purchase #2	$89.34	7.516%	$96.0548	$96.05	$96.05	$96.10
Purchase #3	$37.80	11.284%	$42.0654	$42.07	$42.05	$42.10
Purchase #4	$148.91	7.697%	$160.3716	$160.37	$160.35	$160.40
Purchase #5	$78.99	13.445%	$89.6102	$89.61	$89.60	$89.60
Purchase #6	$93.57	9.202%	$102.1803	$102.18	$102.20	$102.20
Purchase #7	$236.47	8.561%	$256.7142	$256.71	$256.70	$256.70
7 purchase totals =	$733.46		$800.3103	$800.30	$800.25	$800.40