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	$221.71	3.572%	$229.6295	$229.63	$229.65	$229.60
Purchase #2	$75.37	4.715%	$78.9237	$78.92	$78.90	$78.90
Purchase #3	$37.33	13.109%	$42.2236	$42.22	$42.20	$42.20
Purchase #4	$121.33	9.450%	$132.7957	$132.80	$132.80	$132.80
Purchase #5	$38.55	11.825%	$43.1085	$43.11	$43.10	$43.10
Purchase #6	$68.29	8.181%	$73.8768	$73.88	$73.90	$73.90
Purchase #7	$48.25	7.445%	$51.8422	$51.84	$51.85	$51.80
7 purchase totals =	$610.83		$652.4000	$652.40	$652.40	$652.30