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	$56.87	3.488%	$58.8536	$58.85	$58.85	$58.90
Purchase #2	$139.73	12.287%	$156.8986	$156.90	$156.90	$156.90
Purchase #3	$18.27	10.828%	$20.2483	$20.25	$20.25	$20.20
Purchase #4	$35.92	11.471%	$40.0404	$40.04	$40.05	$40.00
Purchase #5	$236.75	8.171%	$256.0948	$256.09	$256.10	$256.10
Purchase #6	$73.85	5.381%	$77.8239	$77.82	$77.80	$77.80
Purchase #7	$148.34	6.200%	$157.5371	$157.54	$157.55	$157.50
7 purchase totals =	$709.73		$767.4967	$767.49	$767.50	$767.40