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	$64.57	8.368%	$69.9732	$69.97	$69.95	$70.00
Purchase #2	$218.25	8.345%	$236.463	$236.46	$236.45	$236.50
Purchase #3	$196.65	11.202%	$218.6787	$218.68	$218.70	$218.70
Purchase #4	$118.93	7.142%	$127.424	$127.42	$127.40	$127.40
Purchase #5	$54.99	8.446%	$59.6345	$59.63	$59.65	$59.60
Purchase #6	$40.28	13.712%	$45.8032	$45.80	$45.80	$45.80
Purchase #7	$195.86	12.574%	$220.4874	$220.49	$220.50	$220.50
7 purchase totals =	$889.53		$978.4640	$978.45	$978.45	$978.50