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	$150.64	10.570%	$166.5626	$166.56	$166.55	$166.60
Purchase #2	$239.68	3.244%	$247.4552	$247.46	$247.45	$247.50
Purchase #3	$213.75	4.621%	$223.6274	$223.63	$223.65	$223.60
Purchase #4	$90.50	11.344%	$100.7663	$100.77	$100.75	$100.80
Purchase #5	$27.45	8.396%	$29.7547	$29.75	$29.75	$29.80
Purchase #6	$90.47	5.850%	$95.7625	$95.76	$95.75	$95.80
Purchase #7	$156.55	9.136%	$170.8524	$170.85	$170.85	$170.90
7 purchase totals =	$969.04		$1,034.7811	$1,034.78	$1,034.75	$1,035.00