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	$212.54	11.550%	$237.0884	$237.09	$237.10	$237.10
Purchase #2	$222.74	12.301%	$250.1392	$250.14	$250.15	$250.10
Purchase #3	$77.73	6.724%	$82.9566	$82.96	$82.95	$83.00
Purchase #4	$139.87	12.140%	$156.8502	$156.85	$156.85	$156.90
Purchase #5	$41.97	10.736%	$46.4759	$46.48	$46.50	$46.50
Purchase #6	$36.50	5.404%	$38.4725	$38.47	$38.45	$38.50
Purchase #7	$250.93	9.718%	$275.3154	$275.32	$275.30	$275.30
7 purchase totals =	$982.28		$1,087.2982	$1,087.31	$1,087.30	$1,087.40