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	$152.29	13.461%	$172.7898	$172.79	$172.80	$172.80
Purchase #2	$126.54	8.570%	$137.3845	$137.38	$137.40	$137.40
Purchase #3	$219.87	11.480%	$245.1111	$245.11	$245.10	$245.10
Purchase #4	$165.33	8.677%	$179.6757	$179.68	$179.70	$179.70
Purchase #5	$144.90	7.640%	$155.9704	$155.97	$155.95	$156.00
Purchase #6	$180.67	4.361%	$188.549	$188.55	$188.55	$188.50
Purchase #7	$49.72	3.644%	$51.5318	$51.53	$51.55	$51.50
7 purchase totals =	$1,039.32		$1,131.0123	$1,131.01	$1,131.05	$1,131.00