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	$221.81	6.771%	$236.8288	$236.83	$236.85	$236.80
Purchase #2	$81.71	13.556%	$92.7866	$92.79	$92.80	$92.80
Purchase #3	$83.94	6.571%	$89.4557	$89.46	$89.45	$89.50
Purchase #4	$222.90	8.647%	$242.1742	$242.17	$242.15	$242.20
Purchase #5	$147.50	11.636%	$164.6631	$164.66	$164.65	$164.70
Purchase #6	$55.85	9.413%	$61.1072	$61.11	$61.10	$61.10
Purchase #7	$179.60	3.180%	$185.3113	$185.31	$185.30	$185.30
7 purchase totals =	$993.31		$1,072.3269	$1,072.33	$1,072.30	$1,072.40