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	$54.56	13.636%	$61.9998	$62.00	$62.00	$62.00
Purchase #2	$243.44	5.333%	$256.4227	$256.42	$256.40	$256.40
Purchase #3	$165.25	12.835%	$186.4598	$186.46	$186.45	$186.50
Purchase #4	$141.64	8.524%	$153.7134	$153.71	$153.70	$153.70
Purchase #5	$191.31	10.273%	$210.9633	$210.96	$210.95	$211.00
Purchase #6	$53.61	10.169%	$59.0616	$59.06	$59.05	$59.10
Purchase #7	$123.79	10.824%	$137.189	$137.19	$137.20	$137.20
7 purchase totals =	$973.60		$1,065.8096	$1,065.80	$1,065.75	$1,065.90