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	$217.82	9.139%	$237.7266	$237.73	$237.75	$237.70
Purchase #2	$13.59	12.486%	$15.2868	$15.29	$15.30	$15.30
Purchase #3	$140.55	7.456%	$151.0294	$151.03	$151.05	$151.00
Purchase #4	$154.70	10.720%	$171.2838	$171.28	$171.30	$171.30
Purchase #5	$50.70	4.856%	$53.162	$53.16	$53.15	$53.20
Purchase #6	$162.63	10.533%	$179.7598	$179.76	$179.75	$179.80
Purchase #7	$116.34	10.172%	$128.1741	$128.17	$128.15	$128.20
7 purchase totals =	$856.33		$936.4225	$936.42	$936.45	$936.50