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	$120.45	9.378%	$131.7458	$131.75	$131.75	$131.70
Purchase #2	$136.33	3.147%	$140.6203	$140.62	$140.60	$140.60
Purchase #3	$188.89	13.426%	$214.2504	$214.25	$214.25	$214.30
Purchase #4	$11.62	6.123%	$12.3315	$12.33	$12.35	$12.30
Purchase #5	$52.72	12.674%	$59.4017	$59.40	$59.40	$59.40
Purchase #6	$177.97	13.457%	$201.9194	$201.92	$201.90	$201.90
Purchase #7	$238.81	11.107%	$265.3346	$265.33	$265.35	$265.30
7 purchase totals =	$926.79		$1,025.6037	$1,025.60	$1,025.60	$1,025.50