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	$118.52	7.278%	$127.1459	$127.15	$127.15	$127.10
Purchase #2	$92.62	3.526%	$95.8858	$95.89	$95.90	$95.90
Purchase #3	$31.39	7.133%	$33.629	$33.63	$33.65	$33.60
Purchase #4	$242.61	11.264%	$269.9376	$269.94	$269.95	$269.90
Purchase #5	$116.82	13.280%	$132.3337	$132.33	$132.35	$132.30
Purchase #6	$175.61	3.717%	$182.1374	$182.14	$182.15	$182.10
Purchase #7	$102.72	9.712%	$112.6962	$112.70	$112.70	$112.70
7 purchase totals =	$880.29		$953.7656	$953.78	$953.85	$953.60