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	$237.31	4.467%	$247.9106	$247.91	$247.90	$247.90
Purchase #2	$56.98	4.749%	$59.686	$59.69	$59.70	$59.70
Purchase #3	$93.30	11.719%	$104.2338	$104.23	$104.25	$104.20
Purchase #4	$200.99	7.852%	$216.7717	$216.77	$216.75	$216.80
Purchase #5	$50.50	7.538%	$54.3067	$54.31	$54.30	$54.30
Purchase #6	$88.48	8.697%	$96.1751	$96.18	$96.20	$96.20
Purchase #7	$60.94	10.854%	$67.5544	$67.55	$67.55	$67.60
7 purchase totals =	$788.50		$846.6383	$846.64	$846.65	$846.70