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	$85.92	6.503%	$91.5074	$91.51	$91.50	$91.50
Purchase #2	$71.79	9.765%	$78.8003	$78.80	$78.80	$78.80
Purchase #3	$55.53	4.483%	$58.0194	$58.02	$58.00	$58.00
Purchase #4	$71.66	13.403%	$81.2646	$81.26	$81.25	$81.30
Purchase #5	$136.53	10.798%	$151.2725	$151.27	$151.25	$151.30
Purchase #6	$145.47	13.226%	$164.7099	$164.71	$164.70	$164.70
Purchase #7	$95.79	6.417%	$101.9368	$101.94	$101.95	$101.90
7 purchase totals =	$662.69		$727.5109	$727.51	$727.45	$727.50