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	$11.98	5.246%	$12.6085	$12.61	$12.60	$12.60
Purchase #2	$88.43	7.750%	$95.2833	$95.28	$95.30	$95.30
Purchase #3	$211.73	4.165%	$220.5486	$220.55	$220.55	$220.50
Purchase #4	$204.60	10.524%	$226.1321	$226.13	$226.15	$226.10
Purchase #5	$73.95	5.614%	$78.1016	$78.10	$78.10	$78.10
Purchase #6	$174.89	3.821%	$181.5725	$181.57	$181.55	$181.60
Purchase #7	$126.75	12.306%	$142.3479	$142.35	$142.35	$142.30
7 purchase totals =	$892.33		$956.5945	$956.59	$956.60	$956.50