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	$210.60	5.718%	$222.6421	$222.64	$222.65	$222.60
Purchase #2	$18.83	12.837%	$21.2472	$21.25	$21.25	$21.20
Purchase #3	$16.50	4.674%	$17.2712	$17.27	$17.25	$17.30
Purchase #4	$142.50	11.126%	$158.3546	$158.35	$158.35	$158.40
Purchase #5	$42.59	8.598%	$46.2519	$46.25	$46.25	$46.30
Purchase #6	$100.77	8.170%	$109.0029	$109.00	$109.00	$109.00
Purchase #7	$250.94	12.300%	$281.8056	$281.81	$281.80	$281.80
7 purchase totals =	$782.73		$856.5755	$856.57	$856.55	$856.60