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	$195.30	13.591%	$221.8432	$221.84	$221.85	$221.80
Purchase #2	$119.48	3.756%	$123.9677	$123.97	$123.95	$124.00
Purchase #3	$99.69	5.133%	$104.8071	$104.81	$104.80	$104.80
Purchase #4	$170.78	7.402%	$183.4211	$183.42	$183.40	$183.40
Purchase #5	$35.41	11.235%	$39.3883	$39.39	$39.40	$39.40
Purchase #6	$37.83	12.283%	$42.4767	$42.48	$42.50	$42.50
Purchase #7	$143.84	6.178%	$152.7264	$152.73	$152.75	$152.70
7 purchase totals =	$802.33		$868.6305	$868.64	$868.65	$868.60