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	$95.84	9.559%	$105.0013	$105.00	$105.00	$105.00
Purchase #2	$143.67	5.746%	$151.9253	$151.93	$151.95	$151.90
Purchase #3	$195.38	4.278%	$203.7384	$203.74	$203.75	$203.70
Purchase #4	$88.47	6.417%	$94.1471	$94.15	$94.15	$94.10
Purchase #5	$105.98	5.829%	$112.1576	$112.16	$112.15	$112.20
Purchase #6	$75.50	3.723%	$78.3109	$78.31	$78.30	$78.30
Purchase #7	$34.59	3.669%	$35.8591	$35.86	$35.85	$35.90
7 purchase totals =	$739.43		$781.1397	$781.15	$781.15	$781.10