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	$109.27	9.375%	$119.5141	$119.51	$119.50	$119.50
Purchase #2	$143.36	3.594%	$148.5124	$148.51	$148.50	$148.50
Purchase #3	$60.79	3.652%	$63.0101	$63.01	$63.00	$63.00
Purchase #4	$99.77	5.560%	$105.3172	$105.32	$105.30	$105.30
Purchase #5	$38.97	11.583%	$43.4839	$43.48	$43.50	$43.50
Purchase #6	$61.35	10.574%	$67.8371	$67.84	$67.85	$67.80
Purchase #7	$23.44	11.457%	$26.1255	$26.13	$26.15	$26.10
7 purchase totals =	$536.95		$573.8003	$573.80	$573.80	$573.70