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	$86.95	5.662%	$91.8731	$91.87	$91.85	$91.90
Purchase #2	$103.55	8.582%	$112.4367	$112.44	$112.45	$112.40
Purchase #3	$42.30	6.846%	$45.1959	$45.20	$45.20	$45.20
Purchase #4	$189.39	10.874%	$209.9843	$209.98	$210.00	$210.00
Purchase #5	$97.49	6.641%	$103.9643	$103.96	$103.95	$104.00
Purchase #6	$127.78	3.242%	$131.9226	$131.92	$131.90	$131.90
Purchase #7	$232.61	6.846%	$248.5345	$248.53	$248.55	$248.50
7 purchase totals =	$880.07		$943.9114	$943.90	$943.90	$943.90