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	$43.96	5.328%	$46.3022	$46.30	$46.30	$46.30
Purchase #2	$125.69	9.178%	$137.2258	$137.23	$137.25	$137.20
Purchase #3	$87.64	13.319%	$99.3128	$99.31	$99.30	$99.30
Purchase #4	$69.73	7.216%	$74.7617	$74.76	$74.75	$74.80
Purchase #5	$208.56	11.184%	$231.8854	$231.89	$231.90	$231.90
Purchase #6	$59.88	8.853%	$65.1812	$65.18	$65.20	$65.20
Purchase #7	$98.27	8.807%	$106.9246	$106.92	$106.90	$106.90
7 purchase totals =	$693.73		$761.5937	$761.59	$761.60	$761.60