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	$236.61	9.478%	$259.0359	$259.04	$259.05	$259.00
Purchase #2	$247.91	9.668%	$271.8779	$271.88	$271.90	$271.90
Purchase #3	$137.26	11.213%	$152.651	$152.65	$152.65	$152.70
Purchase #4	$60.63	11.203%	$67.4224	$67.42	$67.40	$67.40
Purchase #5	$18.66	13.838%	$21.2422	$21.24	$21.25	$21.20
Purchase #6	$193.90	7.571%	$208.5802	$208.58	$208.60	$208.60
Purchase #7	$31.83	11.485%	$35.4857	$35.49	$35.50	$35.50
7 purchase totals =	$926.80		$1,016.2953	$1,016.30	$1,016.35	$1,016.30