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	$246.25	6.771%	$262.9236	$262.92	$262.90	$262.90
Purchase #2	$118.28	7.462%	$127.1061	$127.11	$127.10	$127.10
Purchase #3	$168.83	9.823%	$185.4142	$185.41	$185.40	$185.40
Purchase #4	$236.98	10.230%	$261.2231	$261.22	$261.20	$261.20
Purchase #5	$143.61	13.184%	$162.5435	$162.54	$162.55	$162.50
Purchase #6	$45.65	10.572%	$50.4761	$50.48	$50.50	$50.50
Purchase #7	$135.93	5.280%	$143.1071	$143.11	$143.10	$143.10
7 purchase totals =	$1,095.53		$1,192.7937	$1,192.79	$1,192.75	$1,192.70