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	$203.48	3.626%	$210.8582	$210.86	$210.85	$210.90
Purchase #2	$45.35	3.506%	$46.94	$46.94	$46.95	$46.90
Purchase #3	$206.45	6.680%	$220.2409	$220.24	$220.25	$220.20
Purchase #4	$127.48	13.432%	$144.6031	$144.60	$144.60	$144.60
Purchase #5	$156.72	3.413%	$162.0689	$162.07	$162.05	$162.10
Purchase #6	$52.57	13.602%	$59.7206	$59.72	$59.70	$59.70
Purchase #7	$123.76	13.782%	$140.8166	$140.82	$140.80	$140.80
7 purchase totals =	$915.81		$985.2483	$985.25	$985.20	$985.20