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	$246.83	11.693%	$275.6918	$275.69	$275.70	$275.70
Purchase #2	$179.52	13.713%	$204.1376	$204.14	$204.15	$204.10
Purchase #3	$88.38	11.583%	$98.6171	$98.62	$98.60	$98.60
Purchase #4	$195.60	9.200%	$213.5952	$213.60	$213.60	$213.60
Purchase #5	$99.86	5.177%	$105.0298	$105.03	$105.05	$105.00
Purchase #6	$178.72	9.164%	$195.0979	$195.10	$195.10	$195.10
Purchase #7	$35.57	10.665%	$39.3635	$39.36	$39.35	$39.40
7 purchase totals =	$1,024.48		$1,131.5329	$1,131.54	$1,131.55	$1,131.50