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	$185.86	8.435%	$201.5373	$201.54	$201.55	$201.50
Purchase #2	$100.84	11.366%	$112.3015	$112.30	$112.30	$112.30
Purchase #3	$91.83	12.514%	$103.3216	$103.32	$103.30	$103.30
Purchase #4	$242.70	7.838%	$261.7228	$261.72	$261.70	$261.70
Purchase #5	$169.53	3.570%	$175.5822	$175.58	$175.60	$175.60
Purchase #6	$105.45	5.759%	$111.5229	$111.52	$111.50	$111.50
Purchase #7	$38.84	11.802%	$43.4239	$43.42	$43.40	$43.40
7 purchase totals =	$935.05		$1,009.4122	$1,009.40	$1,009.35	$1,009.30