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	$152.61	4.207%	$159.0303	$159.03	$159.05	$159.00
Purchase #2	$70.68	11.697%	$78.9474	$78.95	$78.95	$78.90
Purchase #3	$50.53	8.224%	$54.6856	$54.69	$54.70	$54.70
Purchase #4	$53.55	10.758%	$59.3109	$59.31	$59.30	$59.30
Purchase #5	$135.69	10.636%	$150.122	$150.12	$150.10	$150.10
Purchase #6	$129.91	7.412%	$139.5389	$139.54	$139.55	$139.50
Purchase #7	$159.66	9.347%	$174.5834	$174.58	$174.60	$174.60
7 purchase totals =	$752.63		$816.2185	$816.22	$816.25	$816.10