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	$141.66	6.529%	$150.909	$150.91	$150.90	$150.90
Purchase #2	$62.42	6.323%	$66.3668	$66.37	$66.35	$66.40
Purchase #3	$113.38	8.845%	$123.4085	$123.41	$123.40	$123.40
Purchase #4	$72.63	7.763%	$78.2683	$78.27	$78.25	$78.30
Purchase #5	$186.77	13.358%	$211.7187	$211.72	$211.70	$211.70
Purchase #6	$250.59	4.728%	$262.4379	$262.44	$262.45	$262.40
Purchase #7	$160.74	13.470%	$182.3917	$182.39	$182.40	$182.40
7 purchase totals =	$988.19		$1,075.5009	$1,075.51	$1,075.45	$1,075.50