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	$182.82	4.403%	$190.8696	$190.87	$190.85	$190.90
Purchase #2	$100.74	8.485%	$109.2878	$109.29	$109.30	$109.30
Purchase #3	$84.64	10.567%	$93.5839	$93.58	$93.60	$93.60
Purchase #4	$104.82	9.462%	$114.7381	$114.74	$114.75	$114.70
Purchase #5	$155.64	5.412%	$164.0632	$164.06	$164.05	$164.10
Purchase #6	$148.50	6.588%	$158.2832	$158.28	$158.30	$158.30
Purchase #7	$187.90	13.290%	$212.8719	$212.87	$212.85	$212.90
7 purchase totals =	$965.06		$1,043.6977	$1,043.69	$1,043.70	$1,043.80