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	$246.30	6.464%	$262.2208	$262.22	$262.20	$262.20
Purchase #2	$60.89	8.152%	$65.8538	$65.85	$65.85	$65.90
Purchase #3	$151.69	13.320%	$171.8951	$171.90	$171.90	$171.90
Purchase #4	$139.82	9.294%	$152.8149	$152.81	$152.80	$152.80
Purchase #5	$23.95	5.578%	$25.2859	$25.29	$25.30	$25.30
Purchase #6	$147.34	13.510%	$167.2456	$167.25	$167.25	$167.20
Purchase #7	$162.73	11.587%	$181.5855	$181.59	$181.60	$181.60
7 purchase totals =	$932.72		$1,026.9016	$1,026.91	$1,026.90	$1,026.90