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	$136.93	8.633%	$148.7512	$148.75	$148.75	$148.80
Purchase #2	$223.42	10.783%	$247.5114	$247.51	$247.50	$247.50
Purchase #3	$147.78	3.221%	$152.54	$152.54	$152.55	$152.50
Purchase #4	$115.28	3.150%	$118.9113	$118.91	$118.90	$118.90
Purchase #5	$173.59	6.527%	$184.9202	$184.92	$184.90	$184.90
Purchase #6	$24.61	13.148%	$27.8457	$27.85	$27.85	$27.80
Purchase #7	$140.90	5.364%	$148.4579	$148.46	$148.45	$148.50
7 purchase totals =	$962.51		$1,028.9377	$1,028.94	$1,028.90	$1,028.90