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	$28.72	12.795%	$32.3947	$32.39	$32.40	$32.40
Purchase #2	$18.84	3.666%	$19.5307	$19.53	$19.55	$19.50
Purchase #3	$111.69	11.659%	$124.7119	$124.71	$124.70	$124.70
Purchase #4	$203.69	10.718%	$225.5215	$225.52	$225.50	$225.50
Purchase #5	$141.91	12.503%	$159.653	$159.65	$159.65	$159.70
Purchase #6	$67.87	12.789%	$76.5499	$76.55	$76.55	$76.50
Purchase #7	$132.94	6.794%	$141.9719	$141.97	$141.95	$142.00
7 purchase totals =	$705.66		$780.3336	$780.32	$780.30	$780.30