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	$36.32	4.134%	$37.8215	$37.82	$37.80	$37.80
Purchase #2	$82.96	5.341%	$87.3909	$87.39	$87.40	$87.40
Purchase #3	$46.28	4.406%	$48.3191	$48.32	$48.30	$48.30
Purchase #4	$165.76	3.434%	$171.4522	$171.45	$171.45	$171.50
Purchase #5	$86.49	3.806%	$89.7818	$89.78	$89.80	$89.80
Purchase #6	$152.35	6.218%	$161.8231	$161.82	$161.80	$161.80
Purchase #7	$113.25	10.680%	$125.3451	$125.35	$125.35	$125.30
7 purchase totals =	$683.41		$721.9337	$721.93	$721.90	$721.90