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	$136.38	11.509%	$152.076	$152.08	$152.10	$152.10
Purchase #2	$132.44	5.442%	$139.6474	$139.65	$139.65	$139.60
Purchase #3	$227.40	12.651%	$256.1684	$256.17	$256.15	$256.20
Purchase #4	$179.26	5.781%	$189.623	$189.62	$189.60	$189.60
Purchase #5	$249.74	9.654%	$273.8499	$273.85	$273.85	$273.80
Purchase #6	$5.89	13.847%	$6.7056	$6.71	$6.70	$6.70
Purchase #7	$81.58	7.314%	$87.5468	$87.55	$87.55	$87.50
7 purchase totals =	$1,012.69		$1,105.6171	$1,105.63	$1,105.60	$1,105.50