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	$196.69	11.801%	$219.9014	$219.90	$219.90	$219.90
Purchase #2	$53.99	5.364%	$56.886	$56.89	$56.90	$56.90
Purchase #3	$95.28	12.190%	$106.8946	$106.89	$106.90	$106.90
Purchase #4	$31.34	12.784%	$35.3465	$35.35	$35.35	$35.30
Purchase #5	$175.88	4.316%	$183.471	$183.47	$183.45	$183.50
Purchase #6	$137.44	11.765%	$153.6098	$153.61	$153.60	$153.60
Purchase #7	$109.88	10.675%	$121.6097	$121.61	$121.60	$121.60
7 purchase totals =	$800.50		$877.7190	$877.72	$877.70	$877.70