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	$112.36	3.643%	$116.4533	$116.45	$116.45	$116.50
Purchase #2	$90.45	12.178%	$101.465	$101.47	$101.45	$101.50
Purchase #3	$191.65	9.860%	$210.5467	$210.55	$210.55	$210.50
Purchase #4	$241.82	6.180%	$256.7645	$256.76	$256.75	$256.80
Purchase #5	$90.95	3.397%	$94.0396	$94.04	$94.05	$94.00
Purchase #6	$45.90	3.385%	$47.4537	$47.45	$47.45	$47.50
Purchase #7	$59.70	4.521%	$62.399	$62.40	$62.40	$62.40
7 purchase totals =	$832.83		$889.1218	$889.12	$889.10	$889.20