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	$84.72	13.422%	$96.0911	$96.09	$96.10	$96.10
Purchase #2	$42.49	6.628%	$45.3062	$45.31	$45.30	$45.30
Purchase #3	$37.84	8.787%	$41.165	$41.17	$41.15	$41.20
Purchase #4	$234.88	6.864%	$251.0022	$251.00	$251.00	$251.00
Purchase #5	$236.33	11.546%	$263.6167	$263.62	$263.60	$263.60
Purchase #6	$155.42	4.802%	$162.8833	$162.88	$162.90	$162.90
Purchase #7	$72.58	12.141%	$81.3919	$81.39	$81.40	$81.40
7 purchase totals =	$864.26		$941.4564	$941.46	$941.45	$941.50