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	$112.91	9.549%	$123.6918	$123.69	$123.70	$123.70
Purchase #2	$18.72	7.207%	$20.0692	$20.07	$20.05	$20.10
Purchase #3	$248.87	4.248%	$259.442	$259.44	$259.45	$259.40
Purchase #4	$119.93	11.538%	$133.7675	$133.77	$133.75	$133.80
Purchase #5	$37.91	11.405%	$42.2336	$42.23	$42.25	$42.20
Purchase #6	$237.67	4.603%	$248.61	$248.61	$248.60	$248.60
Purchase #7	$59.90	7.730%	$64.5303	$64.53	$64.55	$64.50
7 purchase totals =	$835.91		$892.3444	$892.34	$892.35	$892.30