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	$77.54	7.563%	$83.4044	$83.40	$83.40	$83.40
Purchase #2	$208.66	8.813%	$227.0492	$227.05	$227.05	$227.00
Purchase #3	$7.36	7.189%	$7.8891	$7.89	$7.90	$7.90
Purchase #4	$112.72	4.541%	$117.8386	$117.84	$117.85	$117.80
Purchase #5	$101.57	12.844%	$114.6157	$114.62	$114.60	$114.60
Purchase #6	$141.81	11.511%	$158.1337	$158.13	$158.15	$158.10
Purchase #7	$149.35	4.816%	$156.5427	$156.54	$156.55	$156.50
7 purchase totals =	$799.01		$865.4734	$865.47	$865.50	$865.30