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	$54.58	5.762%	$57.7249	$57.72	$57.70	$57.70
Purchase #2	$143.71	8.328%	$155.6782	$155.68	$155.70	$155.70
Purchase #3	$40.49	11.803%	$45.269	$45.27	$45.25	$45.30
Purchase #4	$102.66	10.865%	$113.814	$113.81	$113.80	$113.80
Purchase #5	$176.71	7.489%	$189.9438	$189.94	$189.95	$189.90
Purchase #6	$98.96	10.613%	$109.4626	$109.46	$109.45	$109.50
Purchase #7	$167.78	5.836%	$177.5716	$177.57	$177.55	$177.60
7 purchase totals =	$784.89		$849.4641	$849.45	$849.40	$849.50