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	$107.86	10.635%	$119.3309	$119.33	$119.35	$119.30
Purchase #2	$188.29	12.702%	$212.2066	$212.21	$212.20	$212.20
Purchase #3	$41.75	6.492%	$44.4604	$44.46	$44.45	$44.50
Purchase #4	$80.62	12.197%	$90.4532	$90.45	$90.45	$90.50
Purchase #5	$97.92	11.703%	$109.3796	$109.38	$109.40	$109.40
Purchase #6	$39.34	4.600%	$41.1496	$41.15	$41.15	$41.10
Purchase #7	$189.96	4.552%	$198.607	$198.61	$198.60	$198.60
7 purchase totals =	$745.74		$815.5873	$815.59	$815.60	$815.60