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	$205.94	11.531%	$229.6869	$229.69	$229.70	$229.70
Purchase #2	$211.34	13.552%	$239.9808	$239.98	$240.00	$240.00
Purchase #3	$226.39	8.617%	$245.898	$245.90	$245.90	$245.90
Purchase #4	$18.85	10.606%	$20.8492	$20.85	$20.85	$20.80
Purchase #5	$234.82	3.261%	$242.4775	$242.48	$242.50	$242.50
Purchase #6	$36.88	9.780%	$40.4869	$40.49	$40.50	$40.50
Purchase #7	$55.60	6.733%	$59.3435	$59.34	$59.35	$59.30
7 purchase totals =	$989.82		$1,078.7228	$1,078.73	$1,078.80	$1,078.70