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	$128.81	11.286%	$143.3475	$143.35	$143.35	$143.30
Purchase #2	$209.27	8.406%	$226.8612	$226.86	$226.85	$226.90
Purchase #3	$217.50	5.635%	$229.7561	$229.76	$229.75	$229.80
Purchase #4	$38.99	8.559%	$42.3272	$42.33	$42.35	$42.30
Purchase #5	$64.74	3.307%	$66.881	$66.88	$66.90	$66.90
Purchase #6	$65.45	11.696%	$73.105	$73.11	$73.10	$73.10
Purchase #7	$244.83	12.562%	$275.5855	$275.59	$275.60	$275.60
7 purchase totals =	$969.59		$1,057.8635	$1,057.88	$1,057.90	$1,057.90