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	$224.37	7.594%	$241.4087	$241.41	$241.40	$241.40
Purchase #2	$223.34	12.435%	$251.1123	$251.11	$251.10	$251.10
Purchase #3	$148.73	5.483%	$156.8849	$156.88	$156.90	$156.90
Purchase #4	$19.92	8.346%	$21.5825	$21.58	$21.60	$21.60
Purchase #5	$89.45	11.132%	$99.4076	$99.41	$99.40	$99.40
Purchase #6	$24.83	9.819%	$27.2681	$27.27	$27.25	$27.30
Purchase #7	$11.75	11.534%	$13.1052	$13.11	$13.10	$13.10
7 purchase totals =	$742.39		$810.7693	$810.77	$810.75	$810.80