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	$45.97	3.132%	$47.4098	$47.41	$47.40	$47.40
Purchase #2	$187.56	4.468%	$195.9402	$195.94	$195.95	$195.90
Purchase #3	$37.55	7.584%	$40.3978	$40.40	$40.40	$40.40
Purchase #4	$39.63	10.140%	$43.6485	$43.65	$43.65	$43.60
Purchase #5	$128.86	6.560%	$137.3132	$137.31	$137.30	$137.30
Purchase #6	$67.85	3.780%	$70.4147	$70.41	$70.40	$70.40
Purchase #7	$47.99	11.203%	$53.3663	$53.37	$53.35	$53.40
7 purchase totals =	$555.41		$588.4905	$588.49	$588.45	$588.40