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	$231.82	4.374%	$241.9598	$241.96	$241.95	$242.00
Purchase #2	$77.77	13.769%	$88.4782	$88.48	$88.50	$88.50
Purchase #3	$164.30	6.480%	$174.9466	$174.95	$174.95	$174.90
Purchase #4	$162.33	12.829%	$183.1553	$183.16	$183.15	$183.20
Purchase #5	$220.33	13.365%	$249.7771	$249.78	$249.80	$249.80
Purchase #6	$34.78	9.284%	$38.009	$38.01	$38.00	$38.00
Purchase #7	$38.59	10.542%	$42.6582	$42.66	$42.65	$42.70
7 purchase totals =	$929.92		$1,018.9842	$1,019.00	$1,019.00	$1,019.10