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	$63.32	12.610%	$71.3047	$71.30	$71.30	$71.30
Purchase #2	$160.66	4.215%	$167.4318	$167.43	$167.45	$167.40
Purchase #3	$6.66	10.466%	$7.357	$7.36	$7.35	$7.40
Purchase #4	$86.65	12.498%	$97.4795	$97.48	$97.50	$97.50
Purchase #5	$172.56	12.726%	$194.52	$194.52	$194.50	$194.50
Purchase #6	$43.32	10.459%	$47.8508	$47.85	$47.85	$47.90
Purchase #7	$32.56	11.808%	$36.4047	$36.40	$36.40	$36.40
7 purchase totals =	$565.73		$622.3485	$622.34	$622.35	$622.40