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	$136.55	10.843%	$151.3561	$151.36	$151.35	$151.40
Purchase #2	$12.26	8.841%	$13.3439	$13.34	$13.35	$13.30
Purchase #3	$143.54	9.296%	$156.8835	$156.88	$156.90	$156.90
Purchase #4	$23.83	3.264%	$24.6078	$24.61	$24.60	$24.60
Purchase #5	$41.82	3.672%	$43.3556	$43.36	$43.35	$43.40
Purchase #6	$19.41	4.317%	$20.2479	$20.25	$20.25	$20.20
Purchase #7	$128.28	12.619%	$144.4677	$144.47	$144.45	$144.50
7 purchase totals =	$505.69		$554.2625	$554.27	$554.25	$554.30