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	$194.38	7.188%	$208.352	$208.35	$208.35	$208.40
Purchase #2	$100.94	12.483%	$113.5403	$113.54	$113.55	$113.50
Purchase #3	$41.73	4.147%	$43.4605	$43.46	$43.45	$43.50
Purchase #4	$156.33	8.644%	$169.8432	$169.84	$169.85	$169.80
Purchase #5	$233.27	4.141%	$242.9297	$242.93	$242.95	$242.90
Purchase #6	$107.79	4.680%	$112.8346	$112.83	$112.85	$112.80
Purchase #7	$175.32	13.851%	$199.6036	$199.60	$199.60	$199.60
7 purchase totals =	$1,009.76		$1,090.5639	$1,090.55	$1,090.60	$1,090.50