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	$134.25	5.567%	$141.7237	$141.72	$141.70	$141.70
Purchase #2	$94.90	4.170%	$98.8573	$98.86	$98.85	$98.90
Purchase #3	$170.79	11.736%	$190.8339	$190.83	$190.85	$190.80
Purchase #4	$198.88	11.429%	$221.61	$221.61	$221.60	$221.60
Purchase #5	$138.89	9.865%	$152.5915	$152.59	$152.60	$152.60
Purchase #6	$151.63	10.501%	$167.5527	$167.55	$167.55	$167.60
Purchase #7	$166.74	12.462%	$187.5191	$187.52	$187.50	$187.50
7 purchase totals =	$1,056.08		$1,160.6882	$1,160.68	$1,160.65	$1,160.70