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	$68.39	12.403%	$76.8724	$76.87	$76.85	$76.90
Purchase #2	$98.78	10.232%	$108.8872	$108.89	$108.90	$108.90
Purchase #3	$153.72	7.108%	$164.6464	$164.65	$164.65	$164.60
Purchase #4	$113.50	13.183%	$128.4627	$128.46	$128.45	$128.50
Purchase #5	$141.73	8.568%	$153.8734	$153.87	$153.85	$153.90
Purchase #6	$185.87	5.284%	$195.6914	$195.69	$195.70	$195.70
Purchase #7	$170.50	11.679%	$190.4127	$190.41	$190.40	$190.40
7 purchase totals =	$932.49		$1,018.8462	$1,018.84	$1,018.80	$1,018.90