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	$216.53	3.826%	$224.8144	$224.81	$224.80	$224.80
Purchase #2	$140.88	10.754%	$156.0302	$156.03	$156.05	$156.00
Purchase #3	$143.88	4.416%	$150.2337	$150.23	$150.25	$150.20
Purchase #4	$8.49	4.714%	$8.8902	$8.89	$8.90	$8.90
Purchase #5	$225.61	5.813%	$238.7247	$238.72	$238.70	$238.70
Purchase #6	$210.86	9.380%	$230.6387	$230.64	$230.65	$230.60
Purchase #7	$82.25	4.846%	$86.2358	$86.24	$86.25	$86.20
7 purchase totals =	$1,028.50		$1,095.5677	$1,095.56	$1,095.60	$1,095.40