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	$60.70	7.663%	$65.3514	$65.35	$65.35	$65.40
Purchase #2	$19.58	4.219%	$20.4061	$20.41	$20.40	$20.40
Purchase #3	$222.59	3.436%	$230.2382	$230.24	$230.25	$230.20
Purchase #4	$136.44	11.761%	$152.4867	$152.49	$152.50	$152.50
Purchase #5	$37.76	12.633%	$42.5302	$42.53	$42.55	$42.50
Purchase #6	$86.92	7.757%	$93.6624	$93.66	$93.65	$93.70
Purchase #7	$240.39	12.694%	$270.9051	$270.91	$270.90	$270.90
7 purchase totals =	$804.38		$875.5801	$875.59	$875.60	$875.60