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	$116.73	12.634%	$131.4777	$131.48	$131.50	$131.50
Purchase #2	$228.40	5.743%	$241.517	$241.52	$241.50	$241.50
Purchase #3	$168.60	6.780%	$180.0311	$180.03	$180.05	$180.00
Purchase #4	$44.72	3.589%	$46.325	$46.33	$46.35	$46.30
Purchase #5	$161.57	6.425%	$171.9509	$171.95	$171.95	$172.00
Purchase #6	$142.76	12.115%	$160.0554	$160.06	$160.05	$160.10
Purchase #7	$190.75	12.224%	$214.0673	$214.07	$214.05	$214.10
7 purchase totals =	$1,053.53		$1,145.4244	$1,145.44	$1,145.45	$1,145.50