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	$51.93	3.803%	$53.9049	$53.90	$53.90	$53.90
Purchase #2	$90.31	10.220%	$99.5397	$99.54	$99.55	$99.50
Purchase #3	$240.85	5.815%	$254.8554	$254.86	$254.85	$254.90
Purchase #4	$53.74	10.184%	$59.2129	$59.21	$59.20	$59.20
Purchase #5	$181.76	5.673%	$192.0712	$192.07	$192.05	$192.10
Purchase #6	$145.49	5.693%	$153.7727	$153.77	$153.75	$153.80
Purchase #7	$133.77	7.263%	$143.4857	$143.49	$143.50	$143.50
7 purchase totals =	$897.85		$956.8425	$956.84	$956.80	$956.90