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	$116.96	6.232%	$124.2489	$124.25	$124.25	$124.20
Purchase #2	$75.94	8.811%	$82.6311	$82.63	$82.65	$82.60
Purchase #3	$185.77	4.770%	$194.6312	$194.63	$194.65	$194.60
Purchase #4	$13.90	3.727%	$14.4181	$14.42	$14.40	$14.40
Purchase #5	$64.42	13.169%	$72.9035	$72.90	$72.90	$72.90
Purchase #6	$29.35	4.745%	$30.7427	$30.74	$30.75	$30.70
Purchase #7	$97.38	12.870%	$109.9128	$109.91	$109.90	$109.90
7 purchase totals =	$583.72		$629.4883	$629.48	$629.50	$629.30