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	$38.69	12.622%	$43.5735	$43.57	$43.55	$43.60
Purchase #2	$174.62	7.632%	$187.947	$187.95	$187.95	$187.90
Purchase #3	$89.70	10.152%	$98.8063	$98.81	$98.80	$98.80
Purchase #4	$110.49	8.114%	$119.4552	$119.46	$119.45	$119.50
Purchase #5	$34.57	8.870%	$37.6364	$37.64	$37.65	$37.60
Purchase #6	$63.85	13.408%	$72.411	$72.41	$72.40	$72.40
Purchase #7	$49.98	12.501%	$56.228	$56.23	$56.25	$56.20
7 purchase totals =	$561.90		$616.0574	$616.07	$616.05	$616.00