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	$145.34	11.561%	$162.1428	$162.14	$162.15	$162.10
Purchase #2	$88.83	12.509%	$99.9417	$99.94	$99.95	$99.90
Purchase #3	$165.98	8.727%	$180.4651	$180.47	$180.45	$180.50
Purchase #4	$131.93	12.489%	$148.4067	$148.41	$148.40	$148.40
Purchase #5	$93.51	6.812%	$99.8799	$99.88	$99.90	$99.90
Purchase #6	$123.69	4.494%	$129.2486	$129.25	$129.25	$129.20
Purchase #7	$234.94	11.734%	$262.5079	$262.51	$262.50	$262.50
7 purchase totals =	$984.22		$1,082.5927	$1,082.60	$1,082.60	$1,082.50