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	$181.97	7.849%	$196.2528	$196.25	$196.25	$196.30
Purchase #2	$78.94	5.479%	$83.2651	$83.27	$83.25	$83.30
Purchase #3	$102.75	13.150%	$116.2616	$116.26	$116.25	$116.30
Purchase #4	$89.84	8.202%	$97.2087	$97.21	$97.20	$97.20
Purchase #5	$77.33	3.528%	$80.0582	$80.06	$80.05	$80.10
Purchase #6	$188.25	12.546%	$211.8678	$211.87	$211.85	$211.90
Purchase #7	$160.77	6.680%	$171.5094	$171.51	$171.50	$171.50
7 purchase totals =	$879.85		$956.4236	$956.43	$956.35	$956.60