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	$54.55	9.293%	$59.6193	$59.62	$59.60	$59.60
Purchase #2	$120.83	3.129%	$124.6108	$124.61	$124.60	$124.60
Purchase #3	$238.71	3.601%	$247.3059	$247.31	$247.30	$247.30
Purchase #4	$80.58	8.120%	$87.1231	$87.12	$87.10	$87.10
Purchase #5	$150.32	4.839%	$157.594	$157.59	$157.60	$157.60
Purchase #6	$227.85	5.632%	$240.6825	$240.68	$240.70	$240.70
Purchase #7	$104.50	9.108%	$114.0179	$114.02	$114.00	$114.00
7 purchase totals =	$977.34		$1,030.9535	$1,030.95	$1,030.90	$1,030.90