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	$86.89	6.451%	$92.4953	$92.50	$92.50	$92.50
Purchase #2	$131.53	7.327%	$141.1672	$141.17	$141.15	$141.20
Purchase #3	$15.50	10.569%	$17.1382	$17.14	$17.15	$17.10
Purchase #4	$130.91	5.320%	$137.8744	$137.87	$137.85	$137.90
Purchase #5	$249.38	3.803%	$258.8639	$258.86	$258.85	$258.90
Purchase #6	$113.72	11.586%	$126.8956	$126.90	$126.90	$126.90
Purchase #7	$71.36	10.346%	$78.7429	$78.74	$78.75	$78.70
7 purchase totals =	$799.29		$853.1775	$853.18	$853.15	$853.20