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	$94.47	9.177%	$103.1395	$103.14	$103.15	$103.10
Purchase #2	$157.96	7.485%	$169.7833	$169.78	$169.80	$169.80
Purchase #3	$40.31	6.259%	$42.833	$42.83	$42.85	$42.80
Purchase #4	$129.47	11.165%	$143.9253	$143.93	$143.95	$143.90
Purchase #5	$231.39	4.624%	$242.0895	$242.09	$242.10	$242.10
Purchase #6	$206.64	10.373%	$228.0748	$228.07	$228.05	$228.10
Purchase #7	$140.78	4.153%	$146.6266	$146.63	$146.65	$146.60
7 purchase totals =	$1,001.02		$1,076.4720	$1,076.47	$1,076.55	$1,076.40