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	$210.84	12.490%	$237.1739	$237.17	$237.15	$237.20
Purchase #2	$57.63	13.534%	$65.4296	$65.43	$65.45	$65.40
Purchase #3	$69.25	4.789%	$72.5664	$72.57	$72.55	$72.60
Purchase #4	$173.93	8.561%	$188.8201	$188.82	$188.80	$188.80
Purchase #5	$82.38	9.240%	$89.9919	$89.99	$90.00	$90.00
Purchase #6	$113.71	9.442%	$124.4465	$124.45	$124.45	$124.40
Purchase #7	$24.60	11.172%	$27.3483	$27.35	$27.35	$27.30
7 purchase totals =	$732.34		$805.7767	$805.78	$805.75	$805.70