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	$133.31	7.154%	$142.847	$142.85	$142.85	$142.80
Purchase #2	$129.37	10.407%	$142.8335	$142.83	$142.85	$142.80
Purchase #3	$45.44	8.680%	$49.3842	$49.38	$49.40	$49.40
Purchase #4	$128.81	13.739%	$146.5072	$146.51	$146.50	$146.50
Purchase #5	$51.31	13.306%	$58.1373	$58.14	$58.15	$58.10
Purchase #6	$25.44	11.364%	$28.331	$28.33	$28.35	$28.30
Purchase #7	$48.87	12.559%	$55.0076	$55.01	$55.00	$55.00
7 purchase totals =	$562.55		$623.0478	$623.05	$623.10	$622.90