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	$145.82	13.307%	$165.2243	$165.22	$165.20	$165.20
Purchase #2	$196.87	11.209%	$218.9372	$218.94	$218.95	$218.90
Purchase #3	$22.59	6.305%	$24.0143	$24.01	$24.00	$24.00
Purchase #4	$227.77	7.667%	$245.2331	$245.23	$245.25	$245.20
Purchase #5	$90.69	4.636%	$94.8944	$94.89	$94.90	$94.90
Purchase #6	$168.87	9.706%	$185.2605	$185.26	$185.25	$185.30
Purchase #7	$208.77	8.495%	$226.505	$226.51	$226.50	$226.50
7 purchase totals =	$1,061.38		$1,160.0688	$1,160.06	$1,160.05	$1,160.00