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	$82.29	10.767%	$91.1502	$91.15	$91.15	$91.20
Purchase #2	$76.44	8.124%	$82.65	$82.65	$82.65	$82.70
Purchase #3	$9.53	12.208%	$10.6934	$10.69	$10.70	$10.70
Purchase #4	$229.31	6.223%	$243.58	$243.58	$243.60	$243.60
Purchase #5	$216.42	5.272%	$227.8297	$227.83	$227.85	$227.80
Purchase #6	$199.82	6.476%	$212.7603	$212.76	$212.75	$212.80
Purchase #7	$133.67	6.688%	$142.6098	$142.61	$142.60	$142.60
7 purchase totals =	$947.48		$1,011.2734	$1,011.27	$1,011.30	$1,011.40