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	$172.89	11.783%	$193.2616	$193.26	$193.25	$193.30
Purchase #2	$177.94	11.159%	$197.7963	$197.80	$197.80	$197.80
Purchase #3	$199.39	9.340%	$218.013	$218.01	$218.00	$218.00
Purchase #4	$98.94	6.792%	$105.66	$105.66	$105.65	$105.70
Purchase #5	$123.56	6.456%	$131.537	$131.54	$131.55	$131.50
Purchase #6	$19.66	7.344%	$21.1038	$21.10	$21.10	$21.10
Purchase #7	$96.52	4.602%	$100.9619	$100.96	$100.95	$101.00
7 purchase totals =	$888.90		$968.3336	$968.33	$968.30	$968.40