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	$176.79	10.231%	$194.8774	$194.88	$194.90	$194.90
Purchase #2	$243.35	11.303%	$270.8559	$270.86	$270.85	$270.90
Purchase #3	$17.27	6.258%	$18.3508	$18.35	$18.35	$18.40
Purchase #4	$138.53	3.282%	$143.0766	$143.08	$143.10	$143.10
Purchase #5	$77.28	6.351%	$82.1881	$82.19	$82.20	$82.20
Purchase #6	$213.75	11.584%	$238.5108	$238.51	$238.50	$238.50
Purchase #7	$90.37	10.497%	$99.8561	$99.86	$99.85	$99.90
7 purchase totals =	$957.34		$1,047.7157	$1,047.73	$1,047.75	$1,047.90