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	$94.97	11.496%	$105.8878	$105.89	$105.90	$105.90
Purchase #2	$150.35	5.212%	$158.1862	$158.19	$158.20	$158.20
Purchase #3	$197.90	5.105%	$208.0028	$208.00	$208.00	$208.00
Purchase #4	$153.59	12.850%	$173.3263	$173.33	$173.35	$173.30
Purchase #5	$186.31	10.711%	$206.2657	$206.27	$206.25	$206.30
Purchase #6	$93.69	11.429%	$104.3978	$104.40	$104.40	$104.40
Purchase #7	$50.73	5.721%	$53.6323	$53.63	$53.65	$53.60
7 purchase totals =	$927.54		$1,009.6989	$1,009.71	$1,009.75	$1,009.70