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	$31.67	13.356%	$35.8998	$35.90	$35.90	$35.90
Purchase #2	$67.96	4.826%	$71.2397	$71.24	$71.25	$71.20
Purchase #3	$145.64	11.852%	$162.9013	$162.90	$162.90	$162.90
Purchase #4	$43.67	12.626%	$49.1838	$49.18	$49.20	$49.20
Purchase #5	$236.67	7.743%	$254.9954	$255.00	$255.00	$255.00
Purchase #6	$82.56	10.712%	$91.4038	$91.40	$91.40	$91.40
Purchase #7	$192.69	12.346%	$216.4795	$216.48	$216.50	$216.50
7 purchase totals =	$800.86		$882.1033	$882.10	$882.15	$882.10