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	$85.88	12.495%	$96.6107	$96.61	$96.60	$96.60
Purchase #2	$147.32	5.300%	$155.128	$155.13	$155.15	$155.10
Purchase #3	$225.39	12.556%	$253.69	$253.69	$253.70	$253.70
Purchase #4	$130.38	10.542%	$144.1247	$144.12	$144.10	$144.10
Purchase #5	$134.91	3.709%	$139.9138	$139.91	$139.90	$139.90
Purchase #6	$155.33	11.660%	$173.4415	$173.44	$173.45	$173.40
Purchase #7	$208.72	7.721%	$224.8353	$224.84	$224.85	$224.80
7 purchase totals =	$1,087.93		$1,187.7440	$1,187.74	$1,187.75	$1,187.60