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	10.155%	$202.2886	$202.29	$202.30	$202.30
Purchase #2	$118.53	3.773%	$123.0021	$123.00	$123.00	$123.00
Purchase #3	$122.47	13.574%	$139.0941	$139.09	$139.10	$139.10
Purchase #4	$112.51	13.164%	$127.3208	$127.32	$127.30	$127.30
Purchase #5	$131.54	7.291%	$141.1306	$141.13	$141.15	$141.10
Purchase #6	$31.25	9.213%	$34.1291	$34.13	$34.15	$34.10
Purchase #7	$190.55	4.466%	$199.06	$199.06	$199.05	$199.10
7 purchase totals =	$890.49		$966.0253	$966.02	$966.05	$966.00