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	$132.98	9.400%	$145.4801	$145.48	$145.50	$145.50
Purchase #2	$170.30	13.223%	$192.8188	$192.82	$192.80	$192.80
Purchase #3	$174.75	5.580%	$184.5011	$184.50	$184.50	$184.50
Purchase #4	$211.69	3.167%	$218.3942	$218.39	$218.40	$218.40
Purchase #5	$60.27	13.490%	$68.4004	$68.40	$68.40	$68.40
Purchase #6	$167.41	5.401%	$176.4518	$176.45	$176.45	$176.50
Purchase #7	$51.42	7.185%	$55.1145	$55.11	$55.10	$55.10
7 purchase totals =	$968.82		$1,041.1609	$1,041.15	$1,041.15	$1,041.20