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	$50.83	3.811%	$52.7671	$52.77	$52.75	$52.80
Purchase #2	$233.56	9.440%	$255.6081	$255.61	$255.60	$255.60
Purchase #3	$150.51	4.218%	$156.8585	$156.86	$156.85	$156.90
Purchase #4	$140.74	7.757%	$151.6572	$151.66	$151.65	$151.70
Purchase #5	$163.86	5.525%	$172.9133	$172.91	$172.90	$172.90
Purchase #6	$84.29	12.673%	$94.9721	$94.97	$94.95	$95.00
Purchase #7	$191.37	4.530%	$200.0391	$200.04	$200.05	$200.00
7 purchase totals =	$1,015.16		$1,084.8154	$1,084.82	$1,084.75	$1,084.90