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	$178.94	13.528%	$203.147	$203.15	$203.15	$203.10
Purchase #2	$100.31	13.791%	$114.1438	$114.14	$114.15	$114.10
Purchase #3	$227.65	9.856%	$250.0872	$250.09	$250.10	$250.10
Purchase #4	$53.89	5.464%	$56.8345	$56.83	$56.85	$56.80
Purchase #5	$212.85	5.268%	$224.0629	$224.06	$224.05	$224.10
Purchase #6	$111.61	7.285%	$119.7408	$119.74	$119.75	$119.70
Purchase #7	$39.75	5.493%	$41.9335	$41.93	$41.95	$41.90
7 purchase totals =	$925.00		$1,009.9497	$1,009.94	$1,010.00	$1,009.80