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	$165.71	12.365%	$186.2	$186.20	$186.20	$186.20
Purchase #2	$70.89	9.827%	$77.8564	$77.86	$77.85	$77.90
Purchase #3	$135.31	5.319%	$142.5071	$142.51	$142.50	$142.50
Purchase #4	$195.27	11.352%	$217.4371	$217.44	$217.45	$217.40
Purchase #5	$243.34	13.211%	$275.4876	$275.49	$275.50	$275.50
Purchase #6	$81.94	7.249%	$87.8798	$87.88	$87.90	$87.90
Purchase #7	$185.82	3.697%	$192.6898	$192.69	$192.70	$192.70
7 purchase totals =	$1,078.28		$1,180.0578	$1,180.07	$1,180.10	$1,180.10