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	$114.44	4.500%	$119.5898	$119.59	$119.60	$119.60
Purchase #2	$155.56	12.153%	$174.4652	$174.47	$174.45	$174.50
Purchase #3	$214.33	12.859%	$241.8907	$241.89	$241.90	$241.90
Purchase #4	$184.61	13.609%	$209.7336	$209.73	$209.75	$209.70
Purchase #5	$175.86	10.169%	$193.7432	$193.74	$193.75	$193.70
Purchase #6	$96.72	13.508%	$109.7849	$109.78	$109.80	$109.80
Purchase #7	$40.81	3.623%	$42.2885	$42.29	$42.30	$42.30
7 purchase totals =	$982.33		$1,091.4959	$1,091.49	$1,091.55	$1,091.50