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	$164.40	11.181%	$182.7816	$182.78	$182.80	$182.80
Purchase #2	$241.33	9.575%	$264.4373	$264.44	$264.45	$264.40
Purchase #3	$235.45	11.210%	$261.8439	$261.84	$261.85	$261.80
Purchase #4	$97.70	11.843%	$109.2706	$109.27	$109.25	$109.30
Purchase #5	$63.96	13.191%	$72.397	$72.40	$72.40	$72.40
Purchase #6	$200.50	5.774%	$212.0769	$212.08	$212.10	$212.10
Purchase #7	$38.96	7.164%	$41.7511	$41.75	$41.75	$41.80
7 purchase totals =	$1,042.30		$1,144.5584	$1,144.56	$1,144.60	$1,144.60