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	$235.83	6.574%	$251.3335	$251.33	$251.35	$251.30
Purchase #2	$51.50	5.194%	$54.1749	$54.17	$54.15	$54.20
Purchase #3	$209.34	11.660%	$233.749	$233.75	$233.75	$233.70
Purchase #4	$113.56	5.185%	$119.4481	$119.45	$119.45	$119.40
Purchase #5	$127.79	5.496%	$134.8133	$134.81	$134.80	$134.80
Purchase #6	$47.39	5.164%	$49.8372	$49.84	$49.85	$49.80
Purchase #7	$142.33	11.534%	$158.7463	$158.75	$158.75	$158.70
7 purchase totals =	$927.74		$1,002.1023	$1,002.10	$1,002.10	$1,001.90