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	$116.44	11.760%	$130.1333	$130.13	$130.15	$130.10
Purchase #2	$150.38	5.781%	$159.0735	$159.07	$159.05	$159.10
Purchase #3	$10.99	4.746%	$11.5116	$11.51	$11.50	$11.50
Purchase #4	$160.55	12.514%	$180.6412	$180.64	$180.65	$180.60
Purchase #5	$237.45	4.484%	$248.0973	$248.10	$248.10	$248.10
Purchase #6	$156.37	3.682%	$162.1275	$162.13	$162.15	$162.10
Purchase #7	$83.50	7.323%	$89.6147	$89.61	$89.60	$89.60
7 purchase totals =	$915.68		$981.1991	$981.19	$981.20	$981.10