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	$95.50	5.249%	$100.5128	$100.51	$100.50	$100.50
Purchase #2	$106.39	13.257%	$120.4941	$120.49	$120.50	$120.50
Purchase #3	$205.31	12.744%	$231.4747	$231.47	$231.45	$231.50
Purchase #4	$147.93	4.405%	$154.4463	$154.45	$154.45	$154.40
Purchase #5	$118.47	8.589%	$128.6454	$128.65	$128.65	$128.60
Purchase #6	$155.92	4.363%	$162.7228	$162.72	$162.70	$162.70
Purchase #7	$7.76	3.800%	$8.0549	$8.05	$8.05	$8.10
7 purchase totals =	$837.28		$906.3510	$906.34	$906.30	$906.30