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	$107.39	3.666%	$111.3269	$111.33	$111.35	$111.30
Purchase #2	$122.84	7.300%	$131.8073	$131.81	$131.80	$131.80
Purchase #3	$8.35	4.394%	$8.7169	$8.72	$8.70	$8.70
Purchase #4	$223.97	11.868%	$250.5508	$250.55	$250.55	$250.60
Purchase #5	$120.91	8.315%	$130.9637	$130.96	$130.95	$131.00
Purchase #6	$141.50	8.111%	$152.9771	$152.98	$153.00	$153.00
Purchase #7	$160.72	12.472%	$180.765	$180.77	$180.75	$180.80
7 purchase totals =	$885.68		$967.1077	$967.12	$967.10	$967.20