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	$152.46	6.711%	$162.6916	$162.69	$162.70	$162.70
Purchase #2	$189.67	8.395%	$205.5928	$205.59	$205.60	$205.60
Purchase #3	$78.80	9.850%	$86.5618	$86.56	$86.55	$86.60
Purchase #4	$83.72	9.464%	$91.6433	$91.64	$91.65	$91.60
Purchase #5	$179.71	5.571%	$189.7216	$189.72	$189.70	$189.70
Purchase #6	$246.50	6.223%	$261.8397	$261.84	$261.85	$261.80
Purchase #7	$28.59	10.604%	$31.6217	$31.62	$31.60	$31.60
7 purchase totals =	$959.45		$1,029.6725	$1,029.66	$1,029.65	$1,029.60