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	$185.75	5.633%	$196.2133	$196.21	$196.20	$196.20
Purchase #2	$232.59	7.648%	$250.3785	$250.38	$250.40	$250.40
Purchase #3	$201.42	3.333%	$208.1333	$208.13	$208.15	$208.10
Purchase #4	$229.41	9.311%	$250.7704	$250.77	$250.75	$250.80
Purchase #5	$94.36	6.697%	$100.6793	$100.68	$100.70	$100.70
Purchase #6	$159.83	12.699%	$180.1268	$180.13	$180.15	$180.10
Purchase #7	$64.72	11.451%	$72.1311	$72.13	$72.15	$72.10
7 purchase totals =	$1,168.08		$1,258.4327	$1,258.43	$1,258.50	$1,258.40