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	$138.56	4.548%	$144.8617	$144.86	$144.85	$144.90
Purchase #2	$24.30	7.118%	$26.0297	$26.03	$26.05	$26.00
Purchase #3	$62.27	4.672%	$65.1793	$65.18	$65.20	$65.20
Purchase #4	$188.92	13.334%	$214.1106	$214.11	$214.10	$214.10
Purchase #5	$47.88	6.257%	$50.8759	$50.88	$50.90	$50.90
Purchase #6	$144.58	13.727%	$164.4265	$164.43	$164.45	$164.40
Purchase #7	$71.82	9.834%	$78.8828	$78.88	$78.90	$78.90
7 purchase totals =	$678.33		$744.3665	$744.37	$744.45	$744.40