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	$184.58	6.461%	$196.5057	$196.51	$196.50	$196.50
Purchase #2	$230.88	4.556%	$241.3989	$241.40	$241.40	$241.40
Purchase #3	$154.38	11.336%	$171.8805	$171.88	$171.90	$171.90
Purchase #4	$139.84	7.757%	$150.6874	$150.69	$150.70	$150.70
Purchase #5	$73.45	4.649%	$76.8647	$76.86	$76.85	$76.90
Purchase #6	$245.47	10.114%	$270.2968	$270.30	$270.30	$270.30
Purchase #7	$110.90	8.546%	$120.3775	$120.38	$120.40	$120.40
7 purchase totals =	$1,139.50		$1,228.0115	$1,228.02	$1,228.05	$1,228.10