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	$195.84	10.626%	$216.65	$216.65	$216.65	$216.70
Purchase #2	$95.69	8.206%	$103.5423	$103.54	$103.55	$103.50
Purchase #3	$65.66	9.870%	$72.1406	$72.14	$72.15	$72.10
Purchase #4	$39.94	12.769%	$45.0399	$45.04	$45.05	$45.00
Purchase #5	$172.86	11.114%	$192.0717	$192.07	$192.05	$192.10
Purchase #6	$142.33	7.817%	$153.4559	$153.46	$153.45	$153.50
Purchase #7	$31.84	5.271%	$33.5183	$33.52	$33.50	$33.50
7 purchase totals =	$744.16		$816.4187	$816.42	$816.40	$816.40