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	$143.37	12.310%	$161.0188	$161.02	$161.00	$161.00
Purchase #2	$222.61	7.174%	$238.58	$238.58	$238.60	$238.60
Purchase #3	$116.82	6.711%	$124.6598	$124.66	$124.65	$124.70
Purchase #4	$98.84	12.670%	$111.363	$111.36	$111.35	$111.40
Purchase #5	$119.33	9.193%	$130.3	$130.30	$130.30	$130.30
Purchase #6	$116.87	5.837%	$123.6917	$123.69	$123.70	$123.70
Purchase #7	$164.88	13.357%	$186.903	$186.90	$186.90	$186.90
7 purchase totals =	$982.72		$1,076.5163	$1,076.51	$1,076.50	$1,076.60