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	$166.47	11.595%	$185.7722	$185.77	$185.75	$185.80
Purchase #2	$41.50	5.731%	$43.8784	$43.88	$43.90	$43.90
Purchase #3	$86.91	6.822%	$92.839	$92.84	$92.85	$92.80
Purchase #4	$64.74	4.720%	$67.7957	$67.80	$67.80	$67.80
Purchase #5	$38.44	4.129%	$40.0272	$40.03	$40.05	$40.00
Purchase #6	$211.90	7.542%	$227.8815	$227.88	$227.90	$227.90
Purchase #7	$143.77	9.686%	$157.6956	$157.70	$157.70	$157.70
7 purchase totals =	$753.73		$815.8896	$815.90	$815.95	$815.90