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	$164.81	4.789%	$172.7028	$172.70	$172.70	$172.70
Purchase #2	$106.31	12.633%	$119.7401	$119.74	$119.75	$119.70
Purchase #3	$73.33	7.435%	$78.7821	$78.78	$78.80	$78.80
Purchase #4	$166.78	11.145%	$185.3676	$185.37	$185.35	$185.40
Purchase #5	$66.38	10.350%	$73.2503	$73.25	$73.25	$73.30
Purchase #6	$240.93	13.511%	$273.4821	$273.48	$273.50	$273.50
Purchase #7	$246.61	3.767%	$255.8998	$255.90	$255.90	$255.90
7 purchase totals =	$1,065.15		$1,159.2248	$1,159.22	$1,159.25	$1,159.30