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	$106.63	6.791%	$113.8712	$113.87	$113.85	$113.90
Purchase #2	$152.92	4.421%	$159.6806	$159.68	$159.70	$159.70
Purchase #3	$66.48	7.724%	$71.6149	$71.61	$71.60	$71.60
Purchase #4	$153.48	8.521%	$166.558	$166.56	$166.55	$166.60
Purchase #5	$248.37	12.840%	$280.2607	$280.26	$280.25	$280.30
Purchase #6	$23.41	4.840%	$24.543	$24.54	$24.55	$24.50
Purchase #7	$59.54	13.796%	$67.7541	$67.75	$67.75	$67.80
7 purchase totals =	$810.83		$884.2825	$884.27	$884.25	$884.40