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	$197.55	7.782%	$212.9233	$212.92	$212.90	$212.90
Purchase #2	$161.35	3.795%	$167.4732	$167.47	$167.45	$167.50
Purchase #3	$31.73	9.685%	$34.8031	$34.80	$34.80	$34.80
Purchase #4	$38.42	10.554%	$42.4748	$42.47	$42.45	$42.50
Purchase #5	$150.81	9.830%	$165.6346	$165.63	$165.65	$165.60
Purchase #6	$67.89	6.278%	$72.1521	$72.15	$72.15	$72.20
Purchase #7	$31.80	10.553%	$35.1559	$35.16	$35.15	$35.20
7 purchase totals =	$679.55		$730.6170	$730.60	$730.55	$730.70