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	$208.83	8.811%	$227.23	$227.23	$227.25	$227.20
Purchase #2	$94.98	5.854%	$100.5401	$100.54	$100.55	$100.50
Purchase #3	$218.33	8.649%	$237.2134	$237.21	$237.20	$237.20
Purchase #4	$106.81	4.267%	$111.3676	$111.37	$111.35	$111.40
Purchase #5	$127.76	8.456%	$138.5634	$138.56	$138.55	$138.60
Purchase #6	$250.69	5.234%	$263.8111	$263.81	$263.80	$263.80
Purchase #7	$217.49	11.384%	$242.2491	$242.25	$242.25	$242.20
7 purchase totals =	$1,224.89		$1,320.9747	$1,320.97	$1,320.95	$1,320.90