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	$168.44	4.749%	$176.4392	$176.44	$176.45	$176.40
Purchase #2	$201.74	8.438%	$218.7628	$218.76	$218.75	$218.80
Purchase #3	$82.96	7.751%	$89.3902	$89.39	$89.40	$89.40
Purchase #4	$90.85	13.343%	$102.9721	$102.97	$102.95	$103.00
Purchase #5	$230.64	12.276%	$258.9534	$258.95	$258.95	$259.00
Purchase #6	$141.50	12.193%	$158.7531	$158.75	$158.75	$158.80
Purchase #7	$87.61	13.618%	$99.5407	$99.54	$99.55	$99.50
7 purchase totals =	$1,003.74		$1,104.8115	$1,104.80	$1,104.80	$1,104.90