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	$73.27	10.299%	$80.8161	$80.82	$80.80	$80.80
Purchase #2	$30.49	7.794%	$32.8664	$32.87	$32.85	$32.90
Purchase #3	$32.55	4.543%	$34.0287	$34.03	$34.05	$34.00
Purchase #4	$201.72	8.494%	$218.8541	$218.85	$218.85	$218.90
Purchase #5	$198.38	9.558%	$217.3412	$217.34	$217.35	$217.30
Purchase #6	$179.54	9.496%	$196.5891	$196.59	$196.60	$196.60
Purchase #7	$88.36	5.693%	$93.3903	$93.39	$93.40	$93.40
7 purchase totals =	$804.31		$873.8859	$873.89	$873.90	$873.90