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	$169.98	3.749%	$176.3526	$176.35	$176.35	$176.40
Purchase #2	$137.94	5.843%	$145.9998	$146.00	$146.00	$146.00
Purchase #3	$86.35	4.132%	$89.918	$89.92	$89.90	$89.90
Purchase #4	$107.47	4.711%	$112.5329	$112.53	$112.55	$112.50
Purchase #5	$161.32	4.793%	$169.0521	$169.05	$169.05	$169.10
Purchase #6	$120.26	10.448%	$132.8248	$132.82	$132.80	$132.80
Purchase #7	$165.88	7.622%	$178.5234	$178.52	$178.50	$178.50
7 purchase totals =	$949.20		$1,005.2036	$1,005.19	$1,005.15	$1,005.20