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	$216.90	4.809%	$227.3307	$227.33	$227.35	$227.30
Purchase #2	$237.62	6.699%	$253.5382	$253.54	$253.55	$253.50
Purchase #3	$218.44	4.159%	$227.5249	$227.52	$227.50	$227.50
Purchase #4	$246.44	10.313%	$271.8554	$271.86	$271.85	$271.90
Purchase #5	$33.86	3.664%	$35.1006	$35.10	$35.10	$35.10
Purchase #6	$18.92	6.400%	$20.1309	$20.13	$20.15	$20.10
Purchase #7	$109.43	12.795%	$123.4316	$123.43	$123.45	$123.40
7 purchase totals =	$1,081.61		$1,158.9123	$1,158.91	$1,158.95	$1,158.80