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	$228.27	5.246%	$240.245	$240.25	$240.25	$240.20
Purchase #2	$55.93	9.197%	$61.0739	$61.07	$61.05	$61.10
Purchase #3	$109.74	7.419%	$117.8816	$117.88	$117.90	$117.90
Purchase #4	$164.37	12.744%	$185.3173	$185.32	$185.30	$185.30
Purchase #5	$51.25	3.546%	$53.0673	$53.07	$53.05	$53.10
Purchase #6	$234.75	9.873%	$257.9269	$257.93	$257.95	$257.90
Purchase #7	$245.42	4.538%	$256.5572	$256.56	$256.55	$256.60
7 purchase totals =	$1,089.73		$1,172.0692	$1,172.08	$1,172.05	$1,172.10