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	$43.50	3.637%	$45.0821	$45.08	$45.10	$45.10
Purchase #2	$40.63	12.158%	$45.5698	$45.57	$45.55	$45.60
Purchase #3	$118.44	7.664%	$127.5172	$127.52	$127.50	$127.50
Purchase #4	$198.30	13.212%	$224.4994	$224.50	$224.50	$224.50
Purchase #5	$200.28	3.268%	$206.8252	$206.83	$206.85	$206.80
Purchase #6	$69.97	12.374%	$78.6281	$78.63	$78.65	$78.60
Purchase #7	$178.88	5.336%	$188.425	$188.43	$188.45	$188.40
7 purchase totals =	$850.00		$916.5468	$916.56	$916.60	$916.50