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	$91.52	6.560%	$97.5237	$97.52	$97.50	$97.50
Purchase #2	$30.34	3.514%	$31.4061	$31.41	$31.40	$31.40
Purchase #3	$145.71	4.702%	$152.5613	$152.56	$152.55	$152.60
Purchase #4	$41.67	11.312%	$46.3837	$46.38	$46.40	$46.40
Purchase #5	$144.55	6.836%	$154.4314	$154.43	$154.45	$154.40
Purchase #6	$98.57	6.819%	$105.2915	$105.29	$105.30	$105.30
Purchase #7	$165.45	3.589%	$171.388	$171.39	$171.40	$171.40
7 purchase totals =	$717.81		$758.9857	$758.98	$759.00	$759.00