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	$38.43	8.166%	$41.5682	$41.57	$41.55	$41.60
Purchase #2	$14.70	3.539%	$15.2202	$15.22	$15.20	$15.20
Purchase #3	$159.96	12.480%	$179.923	$179.92	$179.90	$179.90
Purchase #4	$104.78	7.118%	$112.2382	$112.24	$112.25	$112.20
Purchase #5	$62.47	8.112%	$67.5376	$67.54	$67.55	$67.50
Purchase #6	$50.89	4.321%	$53.089	$53.09	$53.10	$53.10
Purchase #7	$228.90	9.121%	$249.778	$249.78	$249.80	$249.80
7 purchase totals =	$660.13		$719.3542	$719.36	$719.35	$719.30