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	$48.39	12.760%	$54.5646	$54.56	$54.55	$54.60
Purchase #2	$225.90	7.516%	$242.8786	$242.88	$242.90	$242.90
Purchase #3	$6.77	10.520%	$7.4822	$7.48	$7.50	$7.50
Purchase #4	$237.28	9.341%	$259.4443	$259.44	$259.45	$259.40
Purchase #5	$79.26	4.451%	$82.7879	$82.79	$82.80	$82.80
Purchase #6	$94.95	10.350%	$104.7773	$104.78	$104.80	$104.80
Purchase #7	$239.99	5.853%	$254.0366	$254.04	$254.05	$254.00
7 purchase totals =	$932.54		$1,005.9715	$1,005.97	$1,006.05	$1,006.00