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	$217.53	9.807%	$238.8632	$238.86	$238.85	$238.90
Purchase #2	$40.90	4.474%	$42.7299	$42.73	$42.75	$42.70
Purchase #3	$143.31	6.691%	$152.8989	$152.90	$152.90	$152.90
Purchase #4	$143.62	11.702%	$160.4264	$160.43	$160.45	$160.40
Purchase #5	$149.77	4.293%	$156.1996	$156.20	$156.20	$156.20
Purchase #6	$96.33	3.303%	$99.5118	$99.51	$99.50	$99.50
Purchase #7	$77.30	7.522%	$83.1145	$83.11	$83.10	$83.10
7 purchase totals =	$868.76		$933.7443	$933.74	$933.75	$933.70