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	$125.94	3.390%	$130.2094	$130.21	$130.20	$130.20
Purchase #2	$115.64	6.820%	$123.5266	$123.53	$123.55	$123.50
Purchase #3	$248.45	12.452%	$279.387	$279.39	$279.40	$279.40
Purchase #4	$88.47	3.226%	$91.324	$91.32	$91.30	$91.30
Purchase #5	$91.59	4.575%	$95.7802	$95.78	$95.80	$95.80
Purchase #6	$51.78	4.321%	$54.0174	$54.02	$54.00	$54.00
Purchase #7	$234.40	6.555%	$249.7649	$249.76	$249.75	$249.80
7 purchase totals =	$956.27		$1,024.0095	$1,024.01	$1,024.00	$1,024.00