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	$45.85	7.762%	$49.4089	$49.41	$49.40	$49.40
Purchase #2	$247.96	7.208%	$265.833	$265.83	$265.85	$265.80
Purchase #3	$114.83	8.709%	$124.8305	$124.83	$124.85	$124.80
Purchase #4	$61.53	9.835%	$67.5815	$67.58	$67.60	$67.60
Purchase #5	$109.52	8.738%	$119.0899	$119.09	$119.10	$119.10
Purchase #6	$249.66	13.765%	$284.0257	$284.03	$284.05	$284.00
Purchase #7	$85.93	4.361%	$89.6774	$89.68	$89.70	$89.70
7 purchase totals =	$915.28		$1,000.4469	$1,000.45	$1,000.55	$1,000.40