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	$105.76	12.633%	$119.1207	$119.12	$119.10	$119.10
Purchase #2	$97.70	10.115%	$107.5824	$107.58	$107.60	$107.60
Purchase #3	$100.71	3.171%	$103.9035	$103.90	$103.90	$103.90
Purchase #4	$150.89	11.800%	$168.695	$168.70	$168.70	$168.70
Purchase #5	$123.90	6.112%	$131.4728	$131.47	$131.45	$131.50
Purchase #6	$216.29	7.294%	$232.0662	$232.07	$232.05	$232.10
Purchase #7	$214.40	6.619%	$228.5911	$228.59	$228.60	$228.60
7 purchase totals =	$1,009.65		$1,091.4317	$1,091.43	$1,091.40	$1,091.50