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	$76.35	12.278%	$85.7243	$85.72	$85.70	$85.70
Purchase #2	$79.83	4.389%	$83.3337	$83.33	$83.35	$83.30
Purchase #3	$213.69	9.168%	$233.2811	$233.28	$233.30	$233.30
Purchase #4	$62.54	7.153%	$67.0135	$67.01	$67.00	$67.00
Purchase #5	$175.90	9.693%	$192.95	$192.95	$192.95	$193.00
Purchase #6	$130.30	10.322%	$143.7496	$143.75	$143.75	$143.70
Purchase #7	$76.90	10.646%	$85.0868	$85.09	$85.10	$85.10
7 purchase totals =	$815.51		$891.1390	$891.13	$891.15	$891.10