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	$41.52	3.225%	$42.859	$42.86	$42.85	$42.90
Purchase #2	$38.69	6.136%	$41.064	$41.06	$41.05	$41.10
Purchase #3	$111.86	7.621%	$120.3849	$120.38	$120.40	$120.40
Purchase #4	$233.61	3.256%	$241.2163	$241.22	$241.20	$241.20
Purchase #5	$223.95	8.480%	$242.941	$242.94	$242.95	$242.90
Purchase #6	$123.50	3.211%	$127.4656	$127.47	$127.45	$127.50
Purchase #7	$177.39	10.258%	$195.5867	$195.59	$195.60	$195.60
7 purchase totals =	$950.52		$1,011.5175	$1,011.52	$1,011.50	$1,011.60