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	$177.29	7.229%	$190.1063	$190.11	$190.10	$190.10
Purchase #2	$186.83	7.329%	$200.5228	$200.52	$200.50	$200.50
Purchase #3	$182.55	11.765%	$204.027	$204.03	$204.05	$204.00
Purchase #4	$44.69	3.128%	$46.0879	$46.09	$46.10	$46.10
Purchase #5	$120.35	9.223%	$131.4499	$131.45	$131.45	$131.40
Purchase #6	$229.57	5.236%	$241.5903	$241.59	$241.60	$241.60
Purchase #7	$162.97	7.832%	$175.7338	$175.73	$175.75	$175.70
7 purchase totals =	$1,104.25		$1,189.5180	$1,189.52	$1,189.55	$1,189.40