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	$216.47	10.323%	$238.8162	$238.82	$238.80	$238.80
Purchase #2	$78.56	3.397%	$81.2287	$81.23	$81.25	$81.20
Purchase #3	$93.42	4.677%	$97.7893	$97.79	$97.80	$97.80
Purchase #4	$81.91	9.143%	$89.399	$89.40	$89.40	$89.40
Purchase #5	$81.38	9.731%	$89.2991	$89.30	$89.30	$89.30
Purchase #6	$129.27	13.584%	$146.83	$146.83	$146.85	$146.80
Purchase #7	$109.38	13.552%	$124.2032	$124.20	$124.20	$124.20
7 purchase totals =	$790.39		$867.5655	$867.57	$867.60	$867.50