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	$155.30	10.421%	$171.4838	$171.48	$171.50	$171.50
Purchase #2	$181.34	6.175%	$192.5377	$192.54	$192.55	$192.50
Purchase #3	$247.27	6.453%	$263.2263	$263.23	$263.25	$263.20
Purchase #4	$44.32	5.780%	$46.8817	$46.88	$46.90	$46.90
Purchase #5	$57.83	7.854%	$62.372	$62.37	$62.35	$62.40
Purchase #6	$217.55	8.734%	$236.5508	$236.55	$236.55	$236.60
Purchase #7	$181.51	5.651%	$191.7671	$191.77	$191.75	$191.80
7 purchase totals =	$1,085.12		$1,164.8194	$1,164.82	$1,164.85	$1,164.90