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	$177.90	4.190%	$185.354	$185.35	$185.35	$185.40
Purchase #2	$246.33	4.273%	$256.8557	$256.86	$256.85	$256.90
Purchase #3	$208.26	3.282%	$215.0951	$215.10	$215.10	$215.10
Purchase #4	$138.46	11.740%	$154.7152	$154.72	$154.70	$154.70
Purchase #5	$54.70	9.177%	$59.7198	$59.72	$59.70	$59.70
Purchase #6	$81.76	5.779%	$86.4849	$86.48	$86.50	$86.50
Purchase #7	$133.99	10.666%	$148.2814	$148.28	$148.30	$148.30
7 purchase totals =	$1,041.40		$1,106.5061	$1,106.51	$1,106.50	$1,106.60