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	$75.93	8.612%	$82.4691	$82.47	$82.45	$82.50
Purchase #2	$78.35	3.391%	$81.0068	$81.01	$81.00	$81.00
Purchase #3	$35.76	10.873%	$39.6482	$39.65	$39.65	$39.60
Purchase #4	$21.75	13.501%	$24.6865	$24.69	$24.70	$24.70
Purchase #5	$137.74	3.189%	$142.1325	$142.13	$142.15	$142.10
Purchase #6	$181.61	9.336%	$198.5651	$198.57	$198.55	$198.60
Purchase #7	$179.47	3.165%	$185.1502	$185.15	$185.15	$185.20
7 purchase totals =	$710.61		$753.6584	$753.67	$753.65	$753.70