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	$104.92	10.640%	$116.0835	$116.08	$116.10	$116.10
Purchase #2	$101.34	7.191%	$108.6274	$108.63	$108.65	$108.60
Purchase #3	$208.65	13.327%	$236.4568	$236.46	$236.45	$236.50
Purchase #4	$83.42	3.401%	$86.2571	$86.26	$86.25	$86.30
Purchase #5	$169.29	7.598%	$182.1527	$182.15	$182.15	$182.20
Purchase #6	$150.77	11.700%	$168.4101	$168.41	$168.40	$168.40
Purchase #7	$10.93	8.216%	$11.828	$11.83	$11.85	$11.80
7 purchase totals =	$829.32		$909.8156	$909.82	$909.85	$909.90