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	$230.82	4.218%	$240.556	$240.56	$240.55	$240.60
Purchase #2	$228.90	9.432%	$250.4898	$250.49	$250.50	$250.50
Purchase #3	$53.79	7.559%	$57.856	$57.86	$57.85	$57.90
Purchase #4	$39.26	12.761%	$44.27	$44.27	$44.25	$44.30
Purchase #5	$219.67	9.653%	$240.8747	$240.87	$240.85	$240.90
Purchase #6	$119.38	10.521%	$131.94	$131.94	$131.95	$131.90
Purchase #7	$132.42	6.174%	$140.5956	$140.60	$140.60	$140.60
7 purchase totals =	$1,024.24		$1,106.5821	$1,106.59	$1,106.55	$1,106.70