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	$241.29	3.809%	$250.4807	$250.48	$250.50	$250.50
Purchase #2	$125.62	13.218%	$142.2245	$142.22	$142.20	$142.20
Purchase #3	$155.66	8.336%	$168.6358	$168.64	$168.65	$168.60
Purchase #4	$120.37	11.777%	$134.546	$134.55	$134.55	$134.50
Purchase #5	$55.44	11.795%	$61.9791	$61.98	$62.00	$62.00
Purchase #6	$234.35	10.770%	$259.5895	$259.59	$259.60	$259.60
Purchase #7	$140.37	4.698%	$146.9646	$146.96	$146.95	$147.00
7 purchase totals =	$1,073.10		$1,164.4202	$1,164.42	$1,164.45	$1,164.40