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	$155.84	7.867%	$168.0999	$168.10	$168.10	$168.10
Purchase #2	$204.48	6.335%	$217.4338	$217.43	$217.45	$217.40
Purchase #3	$114.56	5.383%	$120.7268	$120.73	$120.75	$120.70
Purchase #4	$117.85	8.293%	$127.6233	$127.62	$127.60	$127.60
Purchase #5	$53.55	11.138%	$59.5144	$59.51	$59.50	$59.50
Purchase #6	$22.47	4.506%	$23.4825	$23.48	$23.50	$23.50
Purchase #7	$80.54	11.635%	$89.9108	$89.91	$89.90	$89.90
7 purchase totals =	$749.29		$806.7915	$806.78	$806.80	$806.70