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	$31.85	9.812%	$34.9751	$34.98	$35.00	$35.00
Purchase #2	$248.33	9.818%	$272.711	$272.71	$272.70	$272.70
Purchase #3	$143.82	5.357%	$151.5244	$151.52	$151.50	$151.50
Purchase #4	$184.59	10.172%	$203.3665	$203.37	$203.35	$203.40
Purchase #5	$231.65	5.238%	$243.7838	$243.78	$243.80	$243.80
Purchase #6	$35.53	4.529%	$37.1392	$37.14	$37.15	$37.10
Purchase #7	$224.29	9.521%	$245.6447	$245.64	$245.65	$245.60
7 purchase totals =	$1,100.06		$1,189.1447	$1,189.14	$1,189.15	$1,189.10