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	$218.78	4.291%	$228.1678	$228.17	$228.15	$228.20
Purchase #2	$182.87	11.776%	$204.4048	$204.40	$204.40	$204.40
Purchase #3	$150.51	5.181%	$158.3079	$158.31	$158.30	$158.30
Purchase #4	$39.89	13.839%	$45.4104	$45.41	$45.40	$45.40
Purchase #5	$164.84	3.193%	$170.1033	$170.10	$170.10	$170.10
Purchase #6	$86.89	3.379%	$89.826	$89.83	$89.85	$89.80
Purchase #7	$215.59	4.740%	$225.809	$225.81	$225.80	$225.80
7 purchase totals =	$1,059.37		$1,122.0292	$1,122.03	$1,122.00	$1,122.00