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	$228.46	5.245%	$240.4427	$240.44	$240.45	$240.40
Purchase #2	$245.51	11.311%	$273.2796	$273.28	$273.30	$273.30
Purchase #3	$128.90	7.448%	$138.5005	$138.50	$138.50	$138.50
Purchase #4	$112.50	13.524%	$127.7145	$127.71	$127.70	$127.70
Purchase #5	$49.94	6.194%	$53.0333	$53.03	$53.05	$53.00
Purchase #6	$231.38	8.402%	$250.8205	$250.82	$250.80	$250.80
Purchase #7	$41.85	4.307%	$43.6525	$43.65	$43.65	$43.70
7 purchase totals =	$1,038.54		$1,127.4436	$1,127.43	$1,127.45	$1,127.40