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	$38.65	11.477%	$43.0859	$43.09	$43.10	$43.10
Purchase #2	$96.53	12.352%	$108.4534	$108.45	$108.45	$108.50
Purchase #3	$109.80	4.334%	$114.5587	$114.56	$114.55	$114.60
Purchase #4	$167.96	12.282%	$188.5888	$188.59	$188.60	$188.60
Purchase #5	$92.48	5.709%	$97.7597	$97.76	$97.75	$97.80
Purchase #6	$106.40	10.616%	$117.6954	$117.70	$117.70	$117.70
Purchase #7	$86.82	10.836%	$96.2278	$96.23	$96.25	$96.20
7 purchase totals =	$698.64		$766.3697	$766.38	$766.40	$766.50