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	$95.26	4.625%	$99.6658	$99.67	$99.65	$99.70
Purchase #2	$81.97	10.643%	$90.6941	$90.69	$90.70	$90.70
Purchase #3	$98.83	9.360%	$108.0805	$108.08	$108.10	$108.10
Purchase #4	$108.92	5.257%	$114.6459	$114.65	$114.65	$114.60
Purchase #5	$93.95	8.810%	$102.227	$102.23	$102.25	$102.20
Purchase #6	$213.74	4.263%	$222.8517	$222.85	$222.85	$222.90
Purchase #7	$144.84	13.498%	$164.3905	$164.39	$164.40	$164.40
7 purchase totals =	$837.51		$902.5555	$902.56	$902.60	$902.60