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	$228.62	8.838%	$248.8254	$248.83	$248.85	$248.80
Purchase #2	$49.68	5.365%	$52.3453	$52.35	$52.35	$52.30
Purchase #3	$197.32	6.214%	$209.5815	$209.58	$209.60	$209.60
Purchase #4	$136.86	10.686%	$151.4849	$151.48	$151.50	$151.50
Purchase #5	$92.41	3.351%	$95.5067	$95.51	$95.50	$95.50
Purchase #6	$75.46	3.434%	$78.0513	$78.05	$78.05	$78.10
Purchase #7	$175.48	12.160%	$196.8184	$196.82	$196.80	$196.80
7 purchase totals =	$955.83		$1,032.6135	$1,032.62	$1,032.65	$1,032.60