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	$167.31	6.611%	$178.3709	$178.37	$178.35	$178.40
Purchase #2	$188.67	3.525%	$195.3206	$195.32	$195.30	$195.30
Purchase #3	$109.67	12.596%	$123.484	$123.48	$123.50	$123.50
Purchase #4	$98.88	12.340%	$111.0818	$111.08	$111.10	$111.10
Purchase #5	$124.25	12.511%	$139.7949	$139.79	$139.80	$139.80
Purchase #6	$157.71	13.619%	$179.1885	$179.19	$179.20	$179.20
Purchase #7	$178.51	7.277%	$191.5002	$191.50	$191.50	$191.50
7 purchase totals =	$1,025.00		$1,118.7409	$1,118.73	$1,118.75	$1,118.80