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	$188.76	11.488%	$210.4447	$210.44	$210.45	$210.40
Purchase #2	$48.41	4.192%	$50.4393	$50.44	$50.45	$50.40
Purchase #3	$133.64	8.361%	$144.8136	$144.81	$144.80	$144.80
Purchase #4	$190.38	12.423%	$214.0309	$214.03	$214.05	$214.00
Purchase #5	$203.29	6.601%	$216.7092	$216.71	$216.70	$216.70
Purchase #6	$90.32	9.793%	$99.165	$99.17	$99.15	$99.20
Purchase #7	$101.45	10.329%	$111.9288	$111.93	$111.95	$111.90
7 purchase totals =	$956.25		$1,047.5315	$1,047.53	$1,047.55	$1,047.40