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	$127.92	11.632%	$142.7997	$142.80	$142.80	$142.80
Purchase #2	$245.89	13.667%	$279.4958	$279.50	$279.50	$279.50
Purchase #3	$13.33	8.581%	$14.4738	$14.47	$14.45	$14.50
Purchase #4	$64.50	13.579%	$73.2585	$73.26	$73.25	$73.30
Purchase #5	$168.53	6.580%	$179.6193	$179.62	$179.60	$179.60
Purchase #6	$130.49	6.529%	$139.0097	$139.01	$139.00	$139.00
Purchase #7	$136.65	11.742%	$152.6954	$152.70	$152.70	$152.70
7 purchase totals =	$887.31		$981.3522	$981.36	$981.30	$981.40