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	$101.95	11.690%	$113.868	$113.87	$113.85	$113.90
Purchase #2	$208.69	7.526%	$224.396	$224.40	$224.40	$224.40
Purchase #3	$188.38	4.202%	$196.2957	$196.30	$196.30	$196.30
Purchase #4	$181.32	4.215%	$188.9626	$188.96	$188.95	$189.00
Purchase #5	$204.98	3.541%	$212.2383	$212.24	$212.25	$212.20
Purchase #6	$30.89	6.872%	$33.0128	$33.01	$33.00	$33.00
Purchase #7	$87.69	3.519%	$90.7758	$90.78	$90.80	$90.80
7 purchase totals =	$1,003.90		$1,059.5492	$1,059.56	$1,059.55	$1,059.60