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	$43.33	4.159%	$45.1321	$45.13	$45.15	$45.10
Purchase #2	$203.88	9.137%	$222.5085	$222.51	$222.50	$222.50
Purchase #3	$132.98	11.115%	$147.7607	$147.76	$147.75	$147.80
Purchase #4	$227.28	6.492%	$242.035	$242.04	$242.05	$242.00
Purchase #5	$157.69	9.845%	$173.2146	$173.21	$173.20	$173.20
Purchase #6	$151.32	4.580%	$158.2505	$158.25	$158.25	$158.30
Purchase #7	$222.94	11.727%	$249.0842	$249.08	$249.10	$249.10
7 purchase totals =	$1,139.42		$1,237.9856	$1,237.98	$1,238.00	$1,238.00