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	$239.51	5.745%	$253.2698	$253.27	$253.25	$253.30
Purchase #2	$218.56	12.131%	$245.0735	$245.07	$245.05	$245.10
Purchase #3	$228.40	9.872%	$250.9476	$250.95	$250.95	$250.90
Purchase #4	$92.25	8.435%	$100.0313	$100.03	$100.05	$100.00
Purchase #5	$86.60	10.520%	$95.7103	$95.71	$95.70	$95.70
Purchase #6	$55.39	8.768%	$60.2466	$60.25	$60.25	$60.20
Purchase #7	$164.68	6.164%	$174.8309	$174.83	$174.85	$174.80
7 purchase totals =	$1,085.39		$1,180.1100	$1,180.11	$1,180.10	$1,180.00