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	$36.70	9.126%	$40.0492	$40.05	$40.05	$40.00
Purchase #2	$211.89	10.183%	$233.4668	$233.47	$233.45	$233.50
Purchase #3	$237.72	5.402%	$250.5616	$250.56	$250.55	$250.60
Purchase #4	$132.49	5.204%	$139.3848	$139.38	$139.40	$139.40
Purchase #5	$135.57	6.218%	$143.9997	$144.00	$144.00	$144.00
Purchase #6	$128.61	5.218%	$135.3209	$135.32	$135.30	$135.30
Purchase #7	$140.95	7.629%	$151.7031	$151.70	$151.70	$151.70
7 purchase totals =	$1,023.93		$1,094.4861	$1,094.48	$1,094.45	$1,094.50