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	$31.61	6.851%	$33.7756	$33.78	$33.80	$33.80
Purchase #2	$224.38	5.491%	$236.7007	$236.70	$236.70	$236.70
Purchase #3	$147.81	3.492%	$152.9715	$152.97	$152.95	$153.00
Purchase #4	$95.47	5.266%	$100.4975	$100.50	$100.50	$100.50
Purchase #5	$158.97	6.551%	$169.3841	$169.38	$169.40	$169.40
Purchase #6	$69.34	13.865%	$78.954	$78.95	$78.95	$79.00
Purchase #7	$95.75	10.109%	$105.4294	$105.43	$105.45	$105.40
7 purchase totals =	$823.33		$877.7128	$877.71	$877.75	$877.80