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	$217.67	5.565%	$229.7833	$229.78	$229.80	$229.80
Purchase #2	$17.88	3.427%	$18.4927	$18.49	$18.50	$18.50
Purchase #3	$71.66	8.821%	$77.9811	$77.98	$78.00	$78.00
Purchase #4	$226.50	13.159%	$256.3051	$256.31	$256.30	$256.30
Purchase #5	$69.52	3.300%	$71.8142	$71.81	$71.80	$71.80
Purchase #6	$210.60	6.431%	$224.1437	$224.14	$224.15	$224.10
Purchase #7	$126.57	8.502%	$137.331	$137.33	$137.35	$137.30
7 purchase totals =	$940.40		$1,015.8511	$1,015.84	$1,015.90	$1,015.80