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	$101.57	6.495%	$108.167	$108.17	$108.15	$108.20
Purchase #2	$112.34	13.346%	$127.3329	$127.33	$127.35	$127.30
Purchase #3	$173.26	13.452%	$196.5669	$196.57	$196.55	$196.60
Purchase #4	$248.72	8.641%	$270.2119	$270.21	$270.20	$270.20
Purchase #5	$151.31	10.300%	$166.8949	$166.89	$166.90	$166.90
Purchase #6	$67.47	8.713%	$73.3487	$73.35	$73.35	$73.30
Purchase #7	$89.60	12.496%	$100.7964	$100.80	$100.80	$100.80
7 purchase totals =	$944.27		$1,043.3187	$1,043.32	$1,043.30	$1,043.30