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	$127.58	7.604%	$137.2812	$137.28	$137.30	$137.30
Purchase #2	$77.81	7.558%	$83.6909	$83.69	$83.70	$83.70
Purchase #3	$137.40	8.465%	$149.0309	$149.03	$149.05	$149.00
Purchase #4	$176.53	5.103%	$185.5383	$185.54	$185.55	$185.50
Purchase #5	$172.89	8.585%	$187.7326	$187.73	$187.75	$187.70
Purchase #6	$128.42	11.803%	$143.5774	$143.58	$143.60	$143.60
Purchase #7	$199.41	7.558%	$214.4814	$214.48	$214.50	$214.50
7 purchase totals =	$1,020.04		$1,101.3327	$1,101.33	$1,101.45	$1,101.30