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	$80.45	6.601%	$85.7605	$85.76	$85.75	$85.80
Purchase #2	$37.73	7.425%	$40.5315	$40.53	$40.55	$40.50
Purchase #3	$181.27	8.464%	$196.6127	$196.61	$196.60	$196.60
Purchase #4	$31.36	11.854%	$35.0774	$35.08	$35.10	$35.10
Purchase #5	$73.72	4.121%	$76.758	$76.76	$76.75	$76.80
Purchase #6	$31.97	8.675%	$34.7434	$34.74	$34.75	$34.70
Purchase #7	$225.95	3.294%	$233.3928	$233.39	$233.40	$233.40
7 purchase totals =	$662.45		$702.8763	$702.87	$702.90	$702.90