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	$193.73	12.854%	$218.6321	$218.63	$218.65	$218.60
Purchase #2	$241.41	3.221%	$249.1858	$249.19	$249.20	$249.20
Purchase #3	$36.41	10.329%	$40.1708	$40.17	$40.15	$40.20
Purchase #4	$187.84	4.594%	$196.4694	$196.47	$196.45	$196.50
Purchase #5	$162.72	6.645%	$173.5327	$173.53	$173.55	$173.50
Purchase #6	$182.87	9.673%	$200.559	$200.56	$200.55	$200.60
Purchase #7	$96.77	5.721%	$102.3062	$102.31	$102.30	$102.30
7 purchase totals =	$1,101.75		$1,180.8560	$1,180.86	$1,180.85	$1,180.90