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	$193.78	11.635%	$216.3263	$216.33	$216.35	$216.30
Purchase #2	$39.90	5.526%	$42.1049	$42.10	$42.10	$42.10
Purchase #3	$20.61	4.130%	$21.4612	$21.46	$21.45	$21.50
Purchase #4	$75.61	7.627%	$81.3768	$81.38	$81.40	$81.40
Purchase #5	$136.35	10.179%	$150.2291	$150.23	$150.25	$150.20
Purchase #6	$107.54	11.105%	$119.4823	$119.48	$119.50	$119.50
Purchase #7	$74.46	8.439%	$80.7437	$80.74	$80.75	$80.70
7 purchase totals =	$648.25		$711.7243	$711.72	$711.80	$711.70