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	$176.89	4.229%	$184.3707	$184.37	$184.35	$184.40
Purchase #2	$145.89	4.798%	$152.8898	$152.89	$152.90	$152.90
Purchase #3	$151.34	4.400%	$157.999	$158.00	$158.00	$158.00
Purchase #4	$224.73	9.409%	$245.8748	$245.87	$245.85	$245.90
Purchase #5	$183.87	13.832%	$209.3029	$209.30	$209.30	$209.30
Purchase #6	$94.67	3.817%	$98.2836	$98.28	$98.30	$98.30
Purchase #7	$44.84	13.469%	$50.8795	$50.88	$50.90	$50.90
7 purchase totals =	$1,022.23		$1,099.6003	$1,099.59	$1,099.60	$1,099.70