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	$138.61	3.116%	$142.9291	$142.93	$142.95	$142.90
Purchase #2	$54.39	7.492%	$58.4649	$58.46	$58.45	$58.50
Purchase #3	$29.90	11.554%	$33.3546	$33.35	$33.35	$33.40
Purchase #4	$126.25	5.484%	$133.1736	$133.17	$133.15	$133.20
Purchase #5	$58.75	8.675%	$63.8466	$63.85	$63.85	$63.80
Purchase #6	$189.57	3.573%	$196.3433	$196.34	$196.35	$196.30
Purchase #7	$57.40	13.422%	$65.1042	$65.10	$65.10	$65.10
7 purchase totals =	$654.87		$693.2163	$693.20	$693.20	$693.20