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	$205.99	4.483%	$215.2245	$215.22	$215.20	$215.20
Purchase #2	$110.59	6.572%	$117.858	$117.86	$117.85	$117.90
Purchase #3	$5.94	12.322%	$6.6719	$6.67	$6.65	$6.70
Purchase #4	$137.48	12.411%	$154.5426	$154.54	$154.55	$154.50
Purchase #5	$49.73	12.403%	$55.898	$55.90	$55.90	$55.90
Purchase #6	$229.31	11.269%	$255.1509	$255.15	$255.15	$255.20
Purchase #7	$122.98	3.573%	$127.3741	$127.37	$127.35	$127.40
7 purchase totals =	$862.02		$932.7200	$932.71	$932.65	$932.80