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	$230.70	5.447%	$243.2662	$243.27	$243.25	$243.30
Purchase #2	$136.89	11.301%	$152.3599	$152.36	$152.35	$152.40
Purchase #3	$166.48	3.608%	$172.4866	$172.49	$172.50	$172.50
Purchase #4	$147.45	9.529%	$161.5005	$161.50	$161.50	$161.50
Purchase #5	$195.33	6.577%	$208.1769	$208.18	$208.20	$208.20
Purchase #6	$33.40	4.156%	$34.7881	$34.79	$34.80	$34.80
Purchase #7	$165.96	10.156%	$182.8149	$182.81	$182.80	$182.80
7 purchase totals =	$1,076.21		$1,155.3931	$1,155.40	$1,155.40	$1,155.50