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	$142.52	3.291%	$147.2103	$147.21	$147.20	$147.20
Purchase #2	$18.66	12.307%	$20.9565	$20.96	$20.95	$21.00
Purchase #3	$85.39	4.721%	$89.4213	$89.42	$89.40	$89.40
Purchase #4	$175.82	11.818%	$196.5984	$196.60	$196.60	$196.60
Purchase #5	$202.99	4.383%	$211.8871	$211.89	$211.90	$211.90
Purchase #6	$172.68	11.696%	$192.8767	$192.88	$192.90	$192.90
Purchase #7	$226.42	10.588%	$250.3933	$250.39	$250.40	$250.40
7 purchase totals =	$1,024.48		$1,109.3436	$1,109.35	$1,109.35	$1,109.40