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	$101.84	3.298%	$105.1987	$105.20	$105.20	$105.20
Purchase #2	$246.83	12.103%	$276.7038	$276.70	$276.70	$276.70
Purchase #3	$40.48	6.328%	$43.0416	$43.04	$43.05	$43.00
Purchase #4	$232.47	4.283%	$242.4267	$242.43	$242.45	$242.40
Purchase #5	$165.55	3.661%	$171.6108	$171.61	$171.60	$171.60
Purchase #6	$50.98	3.721%	$52.877	$52.88	$52.90	$52.90
Purchase #7	$120.50	4.508%	$125.9321	$125.93	$125.95	$125.90
7 purchase totals =	$958.65		$1,017.7907	$1,017.79	$1,017.85	$1,017.70