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	$183.64	6.291%	$195.1928	$195.19	$195.20	$195.20
Purchase #2	$45.53	6.829%	$48.6392	$48.64	$48.65	$48.60
Purchase #3	$109.82	6.432%	$116.8836	$116.88	$116.90	$116.90
Purchase #4	$96.39	6.873%	$103.0149	$103.01	$103.00	$103.00
Purchase #5	$116.89	12.265%	$131.2266	$131.23	$131.25	$131.20
Purchase #6	$99.39	7.595%	$106.9387	$106.94	$106.95	$106.90
Purchase #7	$38.33	5.169%	$40.3113	$40.31	$40.30	$40.30
7 purchase totals =	$689.99		$742.2071	$742.20	$742.25	$742.10