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	$135.72	6.221%	$144.1631	$144.16	$144.15	$144.20
Purchase #2	$224.96	7.808%	$242.5249	$242.52	$242.50	$242.50
Purchase #3	$166.97	11.478%	$186.1348	$186.13	$186.15	$186.10
Purchase #4	$201.72	12.192%	$226.3137	$226.31	$226.30	$226.30
Purchase #5	$54.50	5.699%	$57.606	$57.61	$57.60	$57.60
Purchase #6	$244.37	4.678%	$255.8016	$255.80	$255.80	$255.80
Purchase #7	$27.35	9.371%	$29.913	$29.91	$29.90	$29.90
7 purchase totals =	$1,055.59		$1,142.4571	$1,142.44	$1,142.40	$1,142.40