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	$92.39	3.672%	$95.7826	$95.78	$95.80	$95.80
Purchase #2	$36.77	12.508%	$41.3692	$41.37	$41.35	$41.40
Purchase #3	$215.55	6.241%	$229.0025	$229.00	$229.00	$229.00
Purchase #4	$137.31	3.631%	$142.2957	$142.30	$142.30	$142.30
Purchase #5	$249.72	13.764%	$284.0915	$284.09	$284.10	$284.10
Purchase #6	$105.89	3.523%	$109.6205	$109.62	$109.60	$109.60
Purchase #7	$6.50	7.775%	$7.0054	$7.01	$7.00	$7.00
7 purchase totals =	$844.13		$909.1674	$909.17	$909.15	$909.20