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	$98.88	7.113%	$105.9133	$105.91	$105.90	$105.90
Purchase #2	$6.55	11.659%	$7.3137	$7.31	$7.30	$7.30
Purchase #3	$62.50	4.827%	$65.5169	$65.52	$65.50	$65.50
Purchase #4	$131.63	9.331%	$143.9124	$143.91	$143.90	$143.90
Purchase #5	$29.87	11.464%	$33.2943	$33.29	$33.30	$33.30
Purchase #6	$32.90	8.789%	$35.7916	$35.79	$35.80	$35.80
Purchase #7	$233.45	10.131%	$257.1008	$257.10	$257.10	$257.10
7 purchase totals =	$595.78		$648.8430	$648.83	$648.80	$648.80