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	$59.43	13.225%	$67.2896	$67.29	$67.30	$67.30
Purchase #2	$148.93	11.267%	$165.7099	$165.71	$165.70	$165.70
Purchase #3	$229.67	5.581%	$242.4879	$242.49	$242.50	$242.50
Purchase #4	$140.32	7.314%	$150.583	$150.58	$150.60	$150.60
Purchase #5	$83.40	7.332%	$89.5149	$89.51	$89.50	$89.50
Purchase #6	$32.29	11.279%	$35.932	$35.93	$35.95	$35.90
Purchase #7	$233.36	11.424%	$260.019	$260.02	$260.00	$260.00
7 purchase totals =	$927.40		$1,011.5363	$1,011.53	$1,011.55	$1,011.50