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	$100.59	13.580%	$114.2501	$114.25	$114.25	$114.30
Purchase #2	$71.68	9.279%	$78.3312	$78.33	$78.35	$78.30
Purchase #3	$103.43	8.543%	$112.266	$112.27	$112.25	$112.30
Purchase #4	$84.75	13.569%	$96.2497	$96.25	$96.25	$96.20
Purchase #5	$120.43	6.565%	$128.3362	$128.34	$128.35	$128.30
Purchase #6	$123.50	7.292%	$132.5056	$132.51	$132.50	$132.50
Purchase #7	$45.29	9.221%	$49.4662	$49.47	$49.45	$49.50
7 purchase totals =	$649.67		$711.4050	$711.42	$711.40	$711.40