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	$228.27	10.853%	$253.0441	$253.04	$253.05	$253.00
Purchase #2	$112.56	8.639%	$122.2841	$122.28	$122.30	$122.30
Purchase #3	$151.94	12.851%	$171.4658	$171.47	$171.45	$171.50
Purchase #4	$175.63	8.229%	$190.0826	$190.08	$190.10	$190.10
Purchase #5	$72.81	11.476%	$81.1657	$81.17	$81.15	$81.20
Purchase #6	$123.59	10.319%	$136.3433	$136.34	$136.35	$136.30
Purchase #7	$142.70	10.357%	$157.4794	$157.48	$157.50	$157.50
7 purchase totals =	$1,007.50		$1,111.8650	$1,111.86	$1,111.90	$1,111.90