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	$133.43	5.262%	$140.4511	$140.45	$140.45	$140.50
Purchase #2	$175.86	6.652%	$187.5582	$187.56	$187.55	$187.60
Purchase #3	$53.97	10.465%	$59.618	$59.62	$59.60	$59.60
Purchase #4	$39.62	3.471%	$40.9952	$41.00	$41.00	$41.00
Purchase #5	$129.61	10.380%	$143.0635	$143.06	$143.05	$143.10
Purchase #6	$65.93	11.453%	$73.481	$73.48	$73.50	$73.50
Purchase #7	$104.68	4.748%	$109.6502	$109.65	$109.65	$109.70
7 purchase totals =	$703.10		$754.8172	$754.82	$754.80	$755.00