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	$90.43	4.565%	$94.5581	$94.56	$94.55	$94.60
Purchase #2	$126.57	9.176%	$138.1841	$138.18	$138.20	$138.20
Purchase #3	$64.61	12.716%	$72.8258	$72.83	$72.85	$72.80
Purchase #4	$243.89	13.543%	$276.92	$276.92	$276.90	$276.90
Purchase #5	$42.69	3.174%	$44.045	$44.05	$44.05	$44.00
Purchase #6	$16.87	7.451%	$18.127	$18.13	$18.15	$18.10
Purchase #7	$142.80	13.759%	$162.4479	$162.45	$162.45	$162.40
7 purchase totals =	$727.86		$807.1079	$807.12	$807.15	$807.00