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	$132.76	10.836%	$147.1459	$147.15	$147.15	$147.10
Purchase #2	$80.41	11.472%	$89.6346	$89.63	$89.65	$89.60
Purchase #3	$150.90	13.622%	$171.4556	$171.46	$171.45	$171.50
Purchase #4	$114.38	5.620%	$120.8082	$120.81	$120.80	$120.80
Purchase #5	$218.47	9.594%	$239.43	$239.43	$239.45	$239.40
Purchase #6	$217.75	4.221%	$226.9412	$226.94	$226.95	$226.90
Purchase #7	$134.66	13.491%	$152.827	$152.83	$152.85	$152.80
7 purchase totals =	$1,049.33		$1,148.2425	$1,148.25	$1,148.30	$1,148.10