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	$66.53	7.811%	$71.7267	$71.73	$71.75	$71.70
Purchase #2	$177.95	12.826%	$200.7739	$200.77	$200.75	$200.80
Purchase #3	$124.51	4.748%	$130.4217	$130.42	$130.40	$130.40
Purchase #4	$199.54	3.579%	$206.6815	$206.68	$206.70	$206.70
Purchase #5	$81.31	9.580%	$89.0995	$89.10	$89.10	$89.10
Purchase #6	$31.88	5.858%	$33.7475	$33.75	$33.75	$33.70
Purchase #7	$139.61	3.707%	$144.7853	$144.79	$144.80	$144.80
7 purchase totals =	$821.33		$877.2361	$877.24	$877.25	$877.20