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	$160.81	11.723%	$179.6618	$179.66	$179.65	$179.70
Purchase #2	$29.51	10.367%	$32.5693	$32.57	$32.55	$32.60
Purchase #3	$86.30	9.781%	$94.741	$94.74	$94.75	$94.70
Purchase #4	$91.80	8.390%	$99.502	$99.50	$99.50	$99.50
Purchase #5	$155.57	11.825%	$173.9662	$173.97	$173.95	$174.00
Purchase #6	$213.30	8.712%	$231.8827	$231.88	$231.90	$231.90
Purchase #7	$99.53	13.548%	$113.0143	$113.01	$113.00	$113.00
7 purchase totals =	$836.82		$925.3373	$925.33	$925.30	$925.40