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	$52.56	4.310%	$54.8253	$54.83	$54.85	$54.80
Purchase #2	$132.38	3.172%	$136.5791	$136.58	$136.60	$136.60
Purchase #3	$246.59	6.388%	$262.3422	$262.34	$262.35	$262.30
Purchase #4	$28.48	7.269%	$30.5502	$30.55	$30.55	$30.60
Purchase #5	$178.86	3.241%	$184.6569	$184.66	$184.65	$184.70
Purchase #6	$216.96	11.511%	$241.9343	$241.93	$241.95	$241.90
Purchase #7	$94.69	5.520%	$99.9169	$99.92	$99.90	$99.90
7 purchase totals =	$950.52		$1,010.8049	$1,010.81	$1,010.85	$1,010.80