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	$74.97	10.490%	$82.8344	$82.83	$82.85	$82.80
Purchase #2	$95.90	8.465%	$104.0179	$104.02	$104.00	$104.00
Purchase #3	$89.87	5.549%	$94.8569	$94.86	$94.85	$94.90
Purchase #4	$191.50	10.421%	$211.4562	$211.46	$211.45	$211.50
Purchase #5	$220.59	10.787%	$244.385	$244.39	$244.40	$244.40
Purchase #6	$173.35	10.375%	$191.3351	$191.34	$191.35	$191.30
Purchase #7	$32.65	4.304%	$34.0553	$34.06	$34.05	$34.10
7 purchase totals =	$878.83		$962.9408	$962.96	$962.95	$963.00