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	$205.27	12.702%	$231.3434	$231.34	$231.35	$231.30
Purchase #2	$152.64	12.759%	$172.1153	$172.12	$172.10	$172.10
Purchase #3	$77.51	10.248%	$85.4532	$85.45	$85.45	$85.50
Purchase #4	$216.92	9.777%	$238.1283	$238.13	$238.15	$238.10
Purchase #5	$56.29	13.788%	$64.0513	$64.05	$64.05	$64.10
Purchase #6	$211.27	4.473%	$220.7201	$220.72	$220.70	$220.70
Purchase #7	$137.57	3.507%	$142.3946	$142.39	$142.40	$142.40
7 purchase totals =	$1,057.47		$1,154.2062	$1,154.20	$1,154.20	$1,154.20