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	$148.83	4.827%	$156.014	$156.01	$156.00	$156.00
Purchase #2	$231.71	7.684%	$249.5146	$249.51	$249.50	$249.50
Purchase #3	$12.47	12.442%	$14.0215	$14.02	$14.00	$14.00
Purchase #4	$165.62	13.824%	$188.5153	$188.52	$188.50	$188.50
Purchase #5	$189.68	13.624%	$215.522	$215.52	$215.50	$215.50
Purchase #6	$82.57	9.475%	$90.3935	$90.39	$90.40	$90.40
Purchase #7	$186.76	4.662%	$195.4668	$195.47	$195.45	$195.50
7 purchase totals =	$1,017.64		$1,109.4477	$1,109.44	$1,109.35	$1,109.40