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	$137.29	10.468%	$151.6615	$151.66	$151.65	$151.70
Purchase #2	$84.89	5.705%	$89.733	$89.73	$89.75	$89.70
Purchase #3	$5.43	7.452%	$5.8346	$5.83	$5.85	$5.80
Purchase #4	$127.56	10.564%	$141.0354	$141.04	$141.05	$141.00
Purchase #5	$100.93	10.783%	$111.8133	$111.81	$111.80	$111.80
Purchase #6	$156.98	11.392%	$174.8632	$174.86	$174.85	$174.90
Purchase #7	$18.61	6.795%	$19.8745	$19.87	$19.85	$19.90
7 purchase totals =	$631.69		$694.8155	$694.80	$694.80	$694.80