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	$166.96	4.594%	$174.6301	$174.63	$174.65	$174.60
Purchase #2	$151.32	10.721%	$167.543	$167.54	$167.55	$167.50
Purchase #3	$106.45	11.295%	$118.4735	$118.47	$118.45	$118.50
Purchase #4	$40.71	7.317%	$43.6888	$43.69	$43.70	$43.70
Purchase #5	$215.50	3.460%	$222.9563	$222.96	$222.95	$223.00
Purchase #6	$9.62	8.112%	$10.4004	$10.40	$10.40	$10.40
Purchase #7	$148.84	10.839%	$164.9728	$164.97	$164.95	$165.00
7 purchase totals =	$839.40		$902.6649	$902.66	$902.65	$902.70