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	$219.43	9.431%	$240.1244	$240.12	$240.10	$240.10
Purchase #2	$18.95	13.486%	$21.5056	$21.51	$21.50	$21.50
Purchase #3	$81.56	12.203%	$91.5128	$91.51	$91.50	$91.50
Purchase #4	$126.49	8.418%	$137.1379	$137.14	$137.15	$137.10
Purchase #5	$77.75	5.631%	$82.1281	$82.13	$82.15	$82.10
Purchase #6	$68.46	3.389%	$70.7801	$70.78	$70.80	$70.80
Purchase #7	$249.77	5.661%	$263.9095	$263.91	$263.90	$263.90
7 purchase totals =	$842.41		$907.0984	$907.10	$907.10	$907.00