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	$116.86	11.206%	$129.9553	$129.96	$129.95	$130.00
Purchase #2	$163.62	9.563%	$179.267	$179.27	$179.25	$179.30
Purchase #3	$93.32	12.589%	$105.0681	$105.07	$105.05	$105.10
Purchase #4	$151.82	13.629%	$172.5115	$172.51	$172.50	$172.50
Purchase #5	$69.77	3.114%	$71.9426	$71.94	$71.95	$71.90
Purchase #6	$182.82	5.531%	$192.9318	$192.93	$192.95	$192.90
Purchase #7	$223.62	6.775%	$238.7703	$238.77	$238.75	$238.80
7 purchase totals =	$1,001.83		$1,090.4466	$1,090.45	$1,090.40	$1,090.50