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	$64.77	12.631%	$72.9511	$72.95	$72.95	$73.00
Purchase #2	$8.95	11.103%	$9.9437	$9.94	$9.95	$9.90
Purchase #3	$169.56	12.778%	$191.2264	$191.23	$191.25	$191.20
Purchase #4	$158.42	9.710%	$173.8026	$173.80	$173.80	$173.80
Purchase #5	$147.80	10.248%	$162.9465	$162.95	$162.95	$162.90
Purchase #6	$82.94	3.194%	$85.5891	$85.59	$85.60	$85.60
Purchase #7	$95.91	3.374%	$99.146	$99.15	$99.15	$99.10
7 purchase totals =	$728.35		$795.6054	$795.61	$795.65	$795.50