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	$67.64	10.317%	$74.6184	$74.62	$74.60	$74.60
Purchase #2	$63.29	13.605%	$71.9006	$71.90	$71.90	$71.90
Purchase #3	$106.81	8.740%	$116.1452	$116.15	$116.15	$116.10
Purchase #4	$42.59	3.352%	$44.0176	$44.02	$44.00	$44.00
Purchase #5	$9.45	11.741%	$10.5595	$10.56	$10.55	$10.60
Purchase #6	$89.28	8.429%	$96.8054	$96.81	$96.80	$96.80
Purchase #7	$74.74	10.570%	$82.64	$82.64	$82.65	$82.60
7 purchase totals =	$453.80		$496.6867	$496.70	$496.65	$496.60