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	$207.76	11.599%	$231.8581	$231.86	$231.85	$231.90
Purchase #2	$195.46	6.696%	$208.548	$208.55	$208.55	$208.50
Purchase #3	$208.85	3.584%	$216.3352	$216.34	$216.35	$216.30
Purchase #4	$39.43	13.525%	$44.7629	$44.76	$44.75	$44.80
Purchase #5	$65.64	9.518%	$71.8876	$71.89	$71.90	$71.90
Purchase #6	$37.56	3.261%	$38.7848	$38.78	$38.80	$38.80
Purchase #7	$80.79	6.778%	$86.2659	$86.27	$86.25	$86.30
7 purchase totals =	$835.49		$898.4425	$898.45	$898.45	$898.50