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	$147.93	8.663%	$160.7452	$160.75	$160.75	$160.70
Purchase #2	$48.96	7.191%	$52.4807	$52.48	$52.50	$52.50
Purchase #3	$246.99	10.793%	$273.6476	$273.65	$273.65	$273.60
Purchase #4	$112.59	13.397%	$127.6737	$127.67	$127.65	$127.70
Purchase #5	$222.55	12.711%	$250.8383	$250.84	$250.85	$250.80
Purchase #6	$34.65	8.214%	$37.4962	$37.50	$37.50	$37.50
Purchase #7	$79.52	3.859%	$82.5887	$82.59	$82.60	$82.60
7 purchase totals =	$893.19		$985.4704	$985.48	$985.50	$985.40