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	$145.70	3.122%	$150.2488	$150.25	$150.25	$150.20
Purchase #2	$107.43	6.234%	$114.1272	$114.13	$114.15	$114.10
Purchase #3	$103.51	5.238%	$108.9319	$108.93	$108.95	$108.90
Purchase #4	$105.35	13.130%	$119.1825	$119.18	$119.20	$119.20
Purchase #5	$157.36	4.465%	$164.3861	$164.39	$164.40	$164.40
Purchase #6	$149.62	12.669%	$168.5754	$168.58	$168.60	$168.60
Purchase #7	$171.71	10.570%	$189.8597	$189.86	$189.85	$189.90
7 purchase totals =	$940.68		$1,015.3116	$1,015.32	$1,015.40	$1,015.30