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	$236.67	5.622%	$249.9756	$249.98	$250.00	$250.00
Purchase #2	$37.43	3.529%	$38.7509	$38.75	$38.75	$38.80
Purchase #3	$40.90	3.680%	$42.4051	$42.41	$42.40	$42.40
Purchase #4	$40.86	7.388%	$43.8787	$43.88	$43.90	$43.90
Purchase #5	$89.80	12.837%	$101.3276	$101.33	$101.35	$101.30
Purchase #6	$220.69	6.149%	$234.2602	$234.26	$234.25	$234.30
Purchase #7	$145.89	13.190%	$165.1329	$165.13	$165.15	$165.10
7 purchase totals =	$812.24		$875.7310	$875.74	$875.80	$875.80