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	$184.89	12.311%	$207.6518	$207.65	$207.65	$207.70
Purchase #2	$79.43	7.472%	$85.365	$85.37	$85.35	$85.40
Purchase #3	$241.25	11.340%	$268.6078	$268.61	$268.60	$268.60
Purchase #4	$79.90	11.809%	$89.3354	$89.34	$89.35	$89.30
Purchase #5	$47.65	8.342%	$51.625	$51.63	$51.65	$51.60
Purchase #6	$205.59	3.659%	$213.1125	$213.11	$213.10	$213.10
Purchase #7	$81.30	11.648%	$90.7698	$90.77	$90.75	$90.80
7 purchase totals =	$920.01		$1,006.4673	$1,006.48	$1,006.45	$1,006.50