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	$100.81	4.578%	$105.4251	$105.43	$105.45	$105.40
Purchase #2	$136.84	7.531%	$147.1454	$147.15	$147.15	$147.10
Purchase #3	$58.60	7.690%	$63.1063	$63.11	$63.10	$63.10
Purchase #4	$66.37	10.222%	$73.1543	$73.15	$73.15	$73.20
Purchase #5	$223.26	8.146%	$241.4468	$241.45	$241.45	$241.40
Purchase #6	$199.90	11.160%	$222.2088	$222.21	$222.20	$222.20
Purchase #7	$35.30	10.288%	$38.9317	$38.93	$38.95	$38.90
7 purchase totals =	$821.08		$891.4184	$891.43	$891.45	$891.30