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	$116.78	10.312%	$128.8224	$128.82	$128.80	$128.80
Purchase #2	$122.31	10.702%	$135.3996	$135.40	$135.40	$135.40
Purchase #3	$119.31	10.735%	$132.1179	$132.12	$132.10	$132.10
Purchase #4	$249.95	6.215%	$265.4844	$265.48	$265.50	$265.50
Purchase #5	$127.71	11.173%	$141.979	$141.98	$142.00	$142.00
Purchase #6	$53.52	3.637%	$55.4665	$55.47	$55.45	$55.50
Purchase #7	$152.77	9.368%	$167.0815	$167.08	$167.10	$167.10
7 purchase totals =	$942.35		$1,026.3513	$1,026.35	$1,026.35	$1,026.40