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	$142.56	3.755%	$147.9131	$147.91	$147.90	$147.90
Purchase #2	$80.37	9.317%	$87.8581	$87.86	$87.85	$87.90
Purchase #3	$35.65	4.763%	$37.348	$37.35	$37.35	$37.30
Purchase #4	$164.60	12.830%	$185.7182	$185.72	$185.70	$185.70
Purchase #5	$101.64	10.761%	$112.5775	$112.58	$112.60	$112.60
Purchase #6	$30.94	6.466%	$32.9406	$32.94	$32.95	$32.90
Purchase #7	$53.90	7.404%	$57.8908	$57.89	$57.90	$57.90
7 purchase totals =	$609.66		$662.2463	$662.25	$662.25	$662.20