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	$96.45	5.809%	$102.0528	$102.05	$102.05	$102.10
Purchase #2	$5.99	12.466%	$6.7367	$6.74	$6.75	$6.70
Purchase #3	$142.75	6.260%	$151.6862	$151.69	$151.70	$151.70
Purchase #4	$153.58	9.827%	$168.6723	$168.67	$168.65	$168.70
Purchase #5	$52.91	11.529%	$59.01	$59.01	$59.00	$59.00
Purchase #6	$100.89	9.493%	$110.4675	$110.47	$110.45	$110.50
Purchase #7	$99.83	9.571%	$109.3847	$109.38	$109.40	$109.40
7 purchase totals =	$652.40		$708.0102	$708.01	$708.00	$708.10