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	$38.76	6.435%	$41.2542	$41.25	$41.25	$41.30
Purchase #2	$169.64	12.305%	$190.5142	$190.51	$190.50	$190.50
Purchase #3	$68.52	5.425%	$72.2372	$72.24	$72.25	$72.20
Purchase #4	$110.52	8.325%	$119.7208	$119.72	$119.70	$119.70
Purchase #5	$129.38	6.104%	$137.2774	$137.28	$137.30	$137.30
Purchase #6	$165.52	4.370%	$172.7532	$172.75	$172.75	$172.80
Purchase #7	$169.70	12.410%	$190.7598	$190.76	$190.75	$190.80
7 purchase totals =	$852.04		$924.5168	$924.51	$924.50	$924.60