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	$208.74	7.452%	$224.2953	$224.30	$224.30	$224.30
Purchase #2	$137.89	6.465%	$146.8046	$146.80	$146.80	$146.80
Purchase #3	$88.26	13.393%	$100.0807	$100.08	$100.10	$100.10
Purchase #4	$40.33	13.537%	$45.7895	$45.79	$45.80	$45.80
Purchase #5	$24.41	4.397%	$25.4833	$25.48	$25.50	$25.50
Purchase #6	$122.71	6.191%	$130.307	$130.31	$130.30	$130.30
Purchase #7	$36.57	11.474%	$40.766	$40.77	$40.75	$40.80
7 purchase totals =	$658.91		$713.5264	$713.53	$713.55	$713.60