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	$136.87	7.186%	$146.7055	$146.71	$146.70	$146.70
Purchase #2	$158.83	6.411%	$169.0126	$169.01	$169.00	$169.00
Purchase #3	$183.31	3.513%	$189.7497	$189.75	$189.75	$189.70
Purchase #4	$189.75	3.575%	$196.5336	$196.53	$196.55	$196.50
Purchase #5	$196.71	13.169%	$222.6147	$222.61	$222.60	$222.60
Purchase #6	$23.73	8.576%	$25.7651	$25.77	$25.75	$25.80
Purchase #7	$41.66	10.412%	$45.9976	$46.00	$46.00	$46.00
7 purchase totals =	$930.86		$996.3788	$996.38	$996.35	$996.30