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	$142.25	6.104%	$150.9329	$150.93	$150.95	$150.90
Purchase #2	$36.25	7.535%	$38.9814	$38.98	$39.00	$39.00
Purchase #3	$155.83	5.537%	$164.4583	$164.46	$164.45	$164.50
Purchase #4	$139.25	11.144%	$154.768	$154.77	$154.75	$154.80
Purchase #5	$147.37	6.213%	$156.5261	$156.53	$156.55	$156.50
Purchase #6	$151.61	7.412%	$162.8473	$162.85	$162.85	$162.80
Purchase #7	$88.58	3.811%	$91.9558	$91.96	$91.95	$92.00
7 purchase totals =	$861.14		$920.4698	$920.48	$920.50	$920.50