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	$113.79	5.197%	$119.7037	$119.70	$119.70	$119.70
Purchase #2	$41.62	11.379%	$46.3559	$46.36	$46.35	$46.40
Purchase #3	$31.40	3.625%	$32.5383	$32.54	$32.55	$32.50
Purchase #4	$134.94	11.574%	$150.558	$150.56	$150.55	$150.60
Purchase #5	$42.69	7.387%	$45.8435	$45.84	$45.85	$45.80
Purchase #6	$139.50	3.189%	$143.9487	$143.95	$143.95	$143.90
Purchase #7	$35.77	4.721%	$37.4587	$37.46	$37.45	$37.50
7 purchase totals =	$539.71		$576.4068	$576.41	$576.40	$576.40