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	$234.61	3.820%	$243.5721	$243.57	$243.55	$243.60
Purchase #2	$36.59	4.128%	$38.1004	$38.10	$38.10	$38.10
Purchase #3	$152.78	11.557%	$170.4368	$170.44	$170.45	$170.40
Purchase #4	$75.65	3.786%	$78.5141	$78.51	$78.50	$78.50
Purchase #5	$125.47	7.233%	$134.5452	$134.55	$134.55	$134.50
Purchase #6	$146.93	3.465%	$152.0211	$152.02	$152.00	$152.00
Purchase #7	$167.57	7.136%	$179.5278	$179.53	$179.55	$179.50
7 purchase totals =	$939.60		$996.7175	$996.72	$996.70	$996.60