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	$203.83	7.214%	$218.5343	$218.53	$218.55	$218.50
Purchase #2	$95.33	7.727%	$102.6961	$102.70	$102.70	$102.70
Purchase #3	$78.89	3.243%	$81.4484	$81.45	$81.45	$81.40
Purchase #4	$50.74	11.382%	$56.5152	$56.52	$56.50	$56.50
Purchase #5	$74.74	11.744%	$83.5175	$83.52	$83.50	$83.50
Purchase #6	$127.35	5.563%	$134.4345	$134.43	$134.45	$134.40
Purchase #7	$50.94	5.819%	$53.9042	$53.90	$53.90	$53.90
7 purchase totals =	$681.82		$731.0502	$731.05	$731.05	$730.90