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	$11.27	10.527%	$12.4564	$12.46	$12.45	$12.50
Purchase #2	$11.33	10.366%	$12.5045	$12.50	$12.50	$12.50
Purchase #3	$156.39	5.394%	$164.8257	$164.83	$164.85	$164.80
Purchase #4	$11.38	6.477%	$12.1171	$12.12	$12.10	$12.10
Purchase #5	$32.93	12.353%	$36.9978	$37.00	$37.00	$37.00
Purchase #6	$22.44	4.351%	$23.4164	$23.42	$23.40	$23.40
Purchase #7	$99.75	8.807%	$108.535	$108.54	$108.55	$108.50
7 purchase totals =	$345.49		$370.8529	$370.87	$370.85	$370.80