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	$59.39	7.573%	$63.8876	$63.89	$63.90	$63.90
Purchase #2	$138.99	6.111%	$147.4837	$147.48	$147.50	$147.50
Purchase #3	$66.29	7.852%	$71.4951	$71.50	$71.50	$71.50
Purchase #4	$216.57	10.525%	$239.364	$239.36	$239.35	$239.40
Purchase #5	$104.50	9.465%	$114.3909	$114.39	$114.40	$114.40
Purchase #6	$226.77	13.240%	$256.7943	$256.79	$256.80	$256.80
Purchase #7	$148.31	3.627%	$153.6892	$153.69	$153.70	$153.70
7 purchase totals =	$960.82		$1,047.1048	$1,047.10	$1,047.15	$1,047.20