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	$177.38	7.851%	$191.3061	$191.31	$191.30	$191.30
Purchase #2	$60.71	6.169%	$64.4552	$64.46	$64.45	$64.50
Purchase #3	$134.66	11.767%	$150.5054	$150.51	$150.50	$150.50
Purchase #4	$129.46	13.189%	$146.5345	$146.53	$146.55	$146.50
Purchase #5	$218.43	7.510%	$234.8341	$234.83	$234.85	$234.80
Purchase #6	$111.97	3.722%	$116.1375	$116.14	$116.15	$116.10
Purchase #7	$92.75	11.820%	$103.7131	$103.71	$103.70	$103.70
7 purchase totals =	$925.36		$1,007.4859	$1,007.49	$1,007.50	$1,007.40