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	$103.88	7.494%	$111.6648	$111.66	$111.65	$111.70
Purchase #2	$6.71	13.784%	$7.6349	$7.63	$7.65	$7.60
Purchase #3	$222.53	8.791%	$242.0926	$242.09	$242.10	$242.10
Purchase #4	$83.40	10.243%	$91.9427	$91.94	$91.95	$91.90
Purchase #5	$136.47	4.734%	$142.9305	$142.93	$142.95	$142.90
Purchase #6	$165.99	8.700%	$180.4311	$180.43	$180.45	$180.40
Purchase #7	$140.25	4.787%	$146.9638	$146.96	$146.95	$147.00
7 purchase totals =	$859.23		$923.6604	$923.64	$923.70	$923.60