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	$74.92	4.688%	$78.4322	$78.43	$78.45	$78.40
Purchase #2	$81.90	11.613%	$91.411	$91.41	$91.40	$91.40
Purchase #3	$161.59	3.526%	$167.2877	$167.29	$167.30	$167.30
Purchase #4	$49.32	9.216%	$53.8653	$53.87	$53.85	$53.90
Purchase #5	$240.41	9.350%	$262.8883	$262.89	$262.90	$262.90
Purchase #6	$87.83	6.652%	$93.6725	$93.67	$93.65	$93.70
Purchase #7	$211.90	3.364%	$219.0283	$219.03	$219.05	$219.00
7 purchase totals =	$907.87		$966.5853	$966.59	$966.60	$966.60