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	$133.77	9.525%	$146.5116	$146.51	$146.50	$146.50
Purchase #2	$124.51	12.242%	$139.7525	$139.75	$139.75	$139.80
Purchase #3	$67.46	8.592%	$73.2562	$73.26	$73.25	$73.30
Purchase #4	$55.72	7.600%	$59.9547	$59.95	$59.95	$60.00
Purchase #5	$75.61	8.159%	$81.779	$81.78	$81.80	$81.80
Purchase #6	$88.72	7.807%	$95.6464	$95.65	$95.65	$95.60
Purchase #7	$240.93	12.279%	$270.5138	$270.51	$270.50	$270.50
7 purchase totals =	$786.72		$867.4142	$867.41	$867.40	$867.50