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	$117.64	8.695%	$127.8688	$127.87	$127.85	$127.90
Purchase #2	$119.48	7.337%	$128.2462	$128.25	$128.25	$128.20
Purchase #3	$218.81	12.833%	$246.8899	$246.89	$246.90	$246.90
Purchase #4	$199.82	12.393%	$224.5837	$224.58	$224.60	$224.60
Purchase #5	$149.68	8.167%	$161.9044	$161.90	$161.90	$161.90
Purchase #6	$176.33	11.307%	$196.2676	$196.27	$196.25	$196.30
Purchase #7	$152.32	6.527%	$162.2619	$162.26	$162.25	$162.30
7 purchase totals =	$1,134.08		$1,248.0225	$1,248.02	$1,248.00	$1,248.10