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	$116.60	13.392%	$132.2151	$132.22	$132.20	$132.20
Purchase #2	$10.39	9.565%	$11.3838	$11.38	$11.40	$11.40
Purchase #3	$245.73	13.329%	$278.4834	$278.48	$278.50	$278.50
Purchase #4	$215.87	4.389%	$225.3445	$225.34	$225.35	$225.30
Purchase #5	$25.95	7.344%	$27.8558	$27.86	$27.85	$27.90
Purchase #6	$68.27	6.179%	$72.4884	$72.49	$72.50	$72.50
Purchase #7	$18.60	10.107%	$20.4799	$20.48	$20.50	$20.50
7 purchase totals =	$701.41		$768.2509	$768.25	$768.30	$768.30