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	$38.50	8.208%	$41.6601	$41.66	$41.65	$41.70
Purchase #2	$173.36	10.485%	$191.5368	$191.54	$191.55	$191.50
Purchase #3	$168.99	11.522%	$188.461	$188.46	$188.45	$188.50
Purchase #4	$86.96	12.169%	$97.5422	$97.54	$97.55	$97.50
Purchase #5	$154.78	8.785%	$168.3774	$168.38	$168.40	$168.40
Purchase #6	$179.52	4.561%	$187.7079	$187.71	$187.70	$187.70
Purchase #7	$169.50	7.680%	$182.5176	$182.52	$182.50	$182.50
7 purchase totals =	$971.61		$1,057.8030	$1,057.81	$1,057.80	$1,057.80