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	$121.98	4.455%	$127.4142	$127.41	$127.40	$127.40
Purchase #2	$111.52	6.227%	$118.4644	$118.46	$118.45	$118.50
Purchase #3	$231.82	7.581%	$249.3943	$249.39	$249.40	$249.40
Purchase #4	$143.97	11.663%	$160.7612	$160.76	$160.75	$160.80
Purchase #5	$41.43	5.847%	$43.8524	$43.85	$43.85	$43.90
Purchase #6	$166.37	13.789%	$189.3108	$189.31	$189.30	$189.30
Purchase #7	$105.45	8.659%	$114.5809	$114.58	$114.60	$114.60
7 purchase totals =	$922.54		$1,003.7782	$1,003.76	$1,003.75	$1,003.90