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	$181.25	12.385%	$203.6978	$203.70	$203.70	$203.70
Purchase #2	$90.55	5.581%	$95.6036	$95.60	$95.60	$95.60
Purchase #3	$68.27	5.514%	$72.0344	$72.03	$72.05	$72.00
Purchase #4	$51.91	10.518%	$57.3699	$57.37	$57.35	$57.40
Purchase #5	$250.96	5.716%	$265.3049	$265.30	$265.30	$265.30
Purchase #6	$162.98	3.215%	$168.2198	$168.22	$168.20	$168.20
Purchase #7	$238.38	9.781%	$261.6959	$261.70	$261.70	$261.70
7 purchase totals =	$1,044.30		$1,123.9263	$1,123.92	$1,123.90	$1,123.90