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	$167.82	10.368%	$185.2196	$185.22	$185.20	$185.20
Purchase #2	$170.60	9.246%	$186.3737	$186.37	$186.35	$186.40
Purchase #3	$16.72	8.625%	$18.1621	$18.16	$18.15	$18.20
Purchase #4	$111.60	11.659%	$124.6114	$124.61	$124.60	$124.60
Purchase #5	$100.63	5.126%	$105.7883	$105.79	$105.80	$105.80
Purchase #6	$201.38	7.653%	$216.7916	$216.79	$216.80	$216.80
Purchase #7	$240.70	8.410%	$260.9429	$260.94	$260.95	$260.90
7 purchase totals =	$1,009.45		$1,097.8896	$1,097.88	$1,097.85	$1,097.90