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	$53.87	6.488%	$57.3651	$57.37	$57.35	$57.40
Purchase #2	$49.90	5.819%	$52.8037	$52.80	$52.80	$52.80
Purchase #3	$77.66	11.244%	$86.3921	$86.39	$86.40	$86.40
Purchase #4	$250.37	13.868%	$285.0913	$285.09	$285.10	$285.10
Purchase #5	$135.96	4.535%	$142.1258	$142.13	$142.15	$142.10
Purchase #6	$111.54	10.606%	$123.3699	$123.37	$123.35	$123.40
Purchase #7	$21.35	4.423%	$22.2943	$22.29	$22.30	$22.30
7 purchase totals =	$700.65		$769.4422	$769.44	$769.45	$769.50