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	$125.55	13.781%	$142.852	$142.85	$142.85	$142.90
Purchase #2	$32.38	10.158%	$35.6692	$35.67	$35.65	$35.70
Purchase #3	$162.78	5.694%	$172.0487	$172.05	$172.05	$172.00
Purchase #4	$13.80	5.278%	$14.5284	$14.53	$14.55	$14.50
Purchase #5	$19.57	4.323%	$20.416	$20.42	$20.40	$20.40
Purchase #6	$118.80	13.133%	$134.402	$134.40	$134.40	$134.40
Purchase #7	$169.98	6.138%	$180.4134	$180.41	$180.40	$180.40
7 purchase totals =	$642.86		$700.3297	$700.33	$700.30	$700.30