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	$223.74	4.805%	$234.4907	$234.49	$234.50	$234.50
Purchase #2	$178.58	12.137%	$200.2543	$200.25	$200.25	$200.30
Purchase #3	$73.87	9.851%	$81.1469	$81.15	$81.15	$81.10
Purchase #4	$207.99	7.165%	$222.8925	$222.89	$222.90	$222.90
Purchase #5	$112.97	9.576%	$123.788	$123.79	$123.80	$123.80
Purchase #6	$50.70	10.684%	$56.1168	$56.12	$56.10	$56.10
Purchase #7	$169.78	5.231%	$178.6612	$178.66	$178.65	$178.70
7 purchase totals =	$1,017.63		$1,097.3504	$1,097.35	$1,097.35	$1,097.40