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	$168.33	3.282%	$173.8546	$173.85	$173.85	$173.90
Purchase #2	$28.92	11.759%	$32.3207	$32.32	$32.30	$32.30
Purchase #3	$159.79	12.801%	$180.2447	$180.24	$180.25	$180.20
Purchase #4	$168.46	12.757%	$189.9504	$189.95	$189.95	$190.00
Purchase #5	$51.30	3.412%	$53.0504	$53.05	$53.05	$53.10
Purchase #6	$121.98	7.186%	$130.7455	$130.75	$130.75	$130.70
Purchase #7	$49.94	4.750%	$52.3122	$52.31	$52.30	$52.30
7 purchase totals =	$748.72		$812.4785	$812.47	$812.45	$812.50