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	$82.82	7.520%	$89.0481	$89.05	$89.05	$89.00
Purchase #2	$119.50	3.419%	$123.5857	$123.59	$123.60	$123.60
Purchase #3	$47.90	8.654%	$52.0453	$52.05	$52.05	$52.00
Purchase #4	$106.70	3.257%	$110.1752	$110.18	$110.20	$110.20
Purchase #5	$221.82	12.538%	$249.6318	$249.63	$249.65	$249.60
Purchase #6	$185.58	12.730%	$209.2043	$209.20	$209.20	$209.20
Purchase #7	$103.94	7.375%	$111.6056	$111.61	$111.60	$111.60
7 purchase totals =	$868.26		$945.2960	$945.31	$945.35	$945.20