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	$186.40	3.863%	$193.6006	$193.60	$193.60	$193.60
Purchase #2	$162.59	9.155%	$177.4751	$177.48	$177.50	$177.50
Purchase #3	$45.60	3.665%	$47.2712	$47.27	$47.25	$47.30
Purchase #4	$100.70	10.718%	$111.493	$111.49	$111.50	$111.50
Purchase #5	$110.48	8.520%	$119.8929	$119.89	$119.90	$119.90
Purchase #6	$103.85	5.832%	$109.9065	$109.91	$109.90	$109.90
Purchase #7	$247.74	5.506%	$261.3806	$261.38	$261.40	$261.40
7 purchase totals =	$957.36		$1,021.0199	$1,021.02	$1,021.05	$1,021.10