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	$177.33	12.133%	$198.8454	$198.85	$198.85	$198.80
Purchase #2	$245.33	5.124%	$257.9007	$257.90	$257.90	$257.90
Purchase #3	$91.33	8.768%	$99.3378	$99.34	$99.35	$99.30
Purchase #4	$148.91	11.110%	$165.4539	$165.45	$165.45	$165.50
Purchase #5	$49.75	11.816%	$55.6285	$55.63	$55.65	$55.60
Purchase #6	$12.26	13.325%	$13.8936	$13.89	$13.90	$13.90
Purchase #7	$153.66	7.295%	$164.8695	$164.87	$164.85	$164.90
7 purchase totals =	$878.57		$955.9294	$955.93	$955.95	$955.90