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	$226.31	8.635%	$245.8519	$245.85	$245.85	$245.90
Purchase #2	$139.68	5.288%	$147.0663	$147.07	$147.05	$147.10
Purchase #3	$107.67	7.570%	$115.8206	$115.82	$115.80	$115.80
Purchase #4	$126.26	10.211%	$139.1524	$139.15	$139.15	$139.20
Purchase #5	$119.98	13.820%	$136.5612	$136.56	$136.55	$136.60
Purchase #6	$41.65	4.536%	$43.5392	$43.54	$43.55	$43.50
Purchase #7	$187.61	4.623%	$196.2832	$196.28	$196.30	$196.30
7 purchase totals =	$949.16		$1,024.2748	$1,024.27	$1,024.25	$1,024.40