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	$130.80	13.791%	$148.8386	$148.84	$148.85	$148.80
Purchase #2	$152.98	6.369%	$162.7233	$162.72	$162.70	$162.70
Purchase #3	$215.61	11.619%	$240.6617	$240.66	$240.65	$240.70
Purchase #4	$16.92	4.287%	$17.6454	$17.65	$17.65	$17.60
Purchase #5	$55.57	7.717%	$59.8583	$59.86	$59.85	$59.90
Purchase #6	$74.77	7.642%	$80.4839	$80.48	$80.50	$80.50
Purchase #7	$138.45	5.749%	$146.4095	$146.41	$146.40	$146.40
7 purchase totals =	$785.10		$856.6207	$856.62	$856.60	$856.60