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	$153.95	13.766%	$175.1428	$175.14	$175.15	$175.10
Purchase #2	$102.53	13.529%	$116.4013	$116.40	$116.40	$116.40
Purchase #3	$100.28	10.502%	$110.8114	$110.81	$110.80	$110.80
Purchase #4	$134.64	13.168%	$152.3694	$152.37	$152.35	$152.40
Purchase #5	$162.34	10.605%	$179.5562	$179.56	$179.55	$179.60
Purchase #6	$153.81	11.484%	$171.4735	$171.47	$171.45	$171.50
Purchase #7	$67.49	4.285%	$70.3819	$70.38	$70.40	$70.40
7 purchase totals =	$875.04		$976.1365	$976.13	$976.10	$976.20