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	$81.86	13.454%	$92.8734	$92.87	$92.85	$92.90
Purchase #2	$148.30	4.231%	$154.5746	$154.57	$154.55	$154.60
Purchase #3	$193.43	8.387%	$209.653	$209.65	$209.65	$209.70
Purchase #4	$37.80	11.166%	$42.0207	$42.02	$42.00	$42.00
Purchase #5	$178.91	6.717%	$190.9274	$190.93	$190.95	$190.90
Purchase #6	$70.28	12.153%	$78.8211	$78.82	$78.80	$78.80
Purchase #7	$149.67	4.367%	$156.2061	$156.21	$156.20	$156.20
7 purchase totals =	$860.25		$925.0763	$925.07	$925.00	$925.10