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	$207.99	7.528%	$223.6475	$223.65	$223.65	$223.60
Purchase #2	$66.90	12.556%	$75.3	$75.30	$75.30	$75.30
Purchase #3	$98.85	13.788%	$112.4794	$112.48	$112.50	$112.50
Purchase #4	$243.54	11.810%	$272.3021	$272.30	$272.30	$272.30
Purchase #5	$171.59	5.184%	$180.4852	$180.49	$180.50	$180.50
Purchase #6	$79.35	9.124%	$86.5899	$86.59	$86.60	$86.60
Purchase #7	$141.82	12.153%	$159.0554	$159.06	$159.05	$159.10
7 purchase totals =	$1,010.04		$1,109.8595	$1,109.87	$1,109.90	$1,109.90