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	$176.61	8.475%	$191.5777	$191.58	$191.60	$191.60
Purchase #2	$52.37	7.561%	$56.3297	$56.33	$56.35	$56.30
Purchase #3	$113.59	3.160%	$117.1794	$117.18	$117.20	$117.20
Purchase #4	$33.29	6.166%	$35.3427	$35.34	$35.35	$35.30
Purchase #5	$30.75	5.772%	$32.5249	$32.52	$32.50	$32.50
Purchase #6	$13.89	7.466%	$14.927	$14.93	$14.95	$14.90
Purchase #7	$233.91	5.161%	$245.9821	$245.98	$246.00	$246.00
7 purchase totals =	$654.41		$693.8635	$693.86	$693.95	$693.80