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	$132.95	3.216%	$137.2257	$137.23	$137.25	$137.20
Purchase #2	$45.47	3.490%	$47.0569	$47.06	$47.05	$47.10
Purchase #3	$205.40	12.502%	$231.0791	$231.08	$231.10	$231.10
Purchase #4	$42.61	7.602%	$45.8492	$45.85	$45.85	$45.80
Purchase #5	$93.83	5.708%	$99.1858	$99.19	$99.20	$99.20
Purchase #6	$9.29	11.174%	$10.3281	$10.33	$10.35	$10.30
Purchase #7	$128.66	10.781%	$142.5308	$142.53	$142.55	$142.50
7 purchase totals =	$658.21		$713.2556	$713.27	$713.35	$713.20