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	$206.85	8.127%	$223.6607	$223.66	$223.65	$223.70
Purchase #2	$74.75	11.409%	$83.2782	$83.28	$83.30	$83.30
Purchase #3	$158.87	13.222%	$179.8758	$179.88	$179.90	$179.90
Purchase #4	$48.83	9.535%	$53.4859	$53.49	$53.50	$53.50
Purchase #5	$190.80	4.416%	$199.2257	$199.23	$199.25	$199.20
Purchase #6	$106.40	3.820%	$110.4645	$110.46	$110.45	$110.50
Purchase #7	$76.91	7.224%	$82.466	$82.47	$82.45	$82.50
7 purchase totals =	$863.41		$932.4568	$932.47	$932.50	$932.60