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	$203.54	9.476%	$222.8275	$222.83	$222.85	$222.80
Purchase #2	$115.41	9.656%	$126.554	$126.55	$126.55	$126.60
Purchase #3	$86.42	4.844%	$90.6062	$90.61	$90.60	$90.60
Purchase #4	$36.38	13.160%	$41.1676	$41.17	$41.15	$41.20
Purchase #5	$201.81	10.506%	$223.0122	$223.01	$223.00	$223.00
Purchase #6	$62.80	7.854%	$67.7323	$67.73	$67.75	$67.70
Purchase #7	$127.74	6.863%	$136.5068	$136.51	$136.50	$136.50
7 purchase totals =	$834.10		$908.4066	$908.41	$908.40	$908.40