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	$199.60	8.580%	$216.7257	$216.73	$216.75	$216.70
Purchase #2	$152.47	6.171%	$161.8789	$161.88	$161.90	$161.90
Purchase #3	$173.46	10.553%	$191.7652	$191.77	$191.75	$191.80
Purchase #4	$82.88	9.345%	$90.6251	$90.63	$90.65	$90.60
Purchase #5	$40.72	3.773%	$42.2564	$42.26	$42.25	$42.30
Purchase #6	$84.93	7.751%	$91.5129	$91.51	$91.50	$91.50
Purchase #7	$192.26	4.587%	$201.079	$201.08	$201.10	$201.10
7 purchase totals =	$926.32		$995.8432	$995.86	$995.90	$995.90