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	$116.98	13.785%	$133.1057	$133.11	$133.10	$133.10
Purchase #2	$32.43	3.777%	$33.6549	$33.65	$33.65	$33.70
Purchase #3	$40.97	7.129%	$43.8908	$43.89	$43.90	$43.90
Purchase #4	$137.96	3.716%	$143.0866	$143.09	$143.10	$143.10
Purchase #5	$108.86	13.710%	$123.7847	$123.78	$123.80	$123.80
Purchase #6	$100.67	10.196%	$110.9343	$110.93	$110.95	$110.90
Purchase #7	$99.97	9.551%	$109.5181	$109.52	$109.50	$109.50
7 purchase totals =	$637.84		$697.9751	$697.97	$698.00	$698.00