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	$232.68	5.246%	$244.8864	$244.89	$244.90	$244.90
Purchase #2	$168.81	6.657%	$180.0477	$180.05	$180.05	$180.00
Purchase #3	$80.47	3.385%	$83.1939	$83.19	$83.20	$83.20
Purchase #4	$200.89	10.816%	$222.6183	$222.62	$222.60	$222.60
Purchase #5	$111.56	7.468%	$119.8913	$119.89	$119.90	$119.90
Purchase #6	$110.66	5.872%	$117.158	$117.16	$117.15	$117.20
Purchase #7	$147.31	8.217%	$159.4145	$159.41	$159.40	$159.40
7 purchase totals =	$1,052.38		$1,127.2101	$1,127.21	$1,127.20	$1,127.20