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	$190.25	4.828%	$199.4353	$199.44	$199.45	$199.40
Purchase #2	$118.94	12.656%	$133.993	$133.99	$134.00	$134.00
Purchase #3	$215.52	4.385%	$224.9706	$224.97	$224.95	$225.00
Purchase #4	$85.61	4.282%	$89.2758	$89.28	$89.30	$89.30
Purchase #5	$95.39	5.299%	$100.4447	$100.44	$100.45	$100.40
Purchase #6	$80.60	11.576%	$89.9303	$89.93	$89.95	$89.90
Purchase #7	$25.33	13.306%	$28.7004	$28.70	$28.70	$28.70
7 purchase totals =	$811.64		$866.7501	$866.75	$866.80	$866.70