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	$201.73	9.191%	$220.271	$220.27	$220.25	$220.30
Purchase #2	$52.60	4.358%	$54.8923	$54.89	$54.90	$54.90
Purchase #3	$194.66	12.367%	$218.7336	$218.73	$218.75	$218.70
Purchase #4	$162.34	6.486%	$172.8694	$172.87	$172.85	$172.90
Purchase #5	$146.69	10.166%	$161.6025	$161.60	$161.60	$161.60
Purchase #6	$240.78	13.181%	$272.5172	$272.52	$272.50	$272.50
Purchase #7	$67.41	4.542%	$70.4718	$70.47	$70.45	$70.50
7 purchase totals =	$1,066.21		$1,171.3578	$1,171.35	$1,171.30	$1,171.40