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	$180.43	8.723%	$196.1689	$196.17	$196.15	$196.20
Purchase #2	$99.76	8.828%	$108.5668	$108.57	$108.55	$108.60
Purchase #3	$207.76	7.541%	$223.4272	$223.43	$223.45	$223.40
Purchase #4	$84.51	6.863%	$90.3099	$90.31	$90.30	$90.30
Purchase #5	$229.70	8.380%	$248.9489	$248.95	$248.95	$248.90
Purchase #6	$189.53	12.726%	$213.6496	$213.65	$213.65	$213.60
Purchase #7	$248.40	9.658%	$272.3905	$272.39	$272.40	$272.40
7 purchase totals =	$1,240.09		$1,353.4618	$1,353.47	$1,353.45	$1,353.40