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	$136.53	11.710%	$152.5177	$152.52	$152.50	$152.50
Purchase #2	$8.28	9.327%	$9.0523	$9.05	$9.05	$9.10
Purchase #3	$173.52	3.679%	$179.9038	$179.90	$179.90	$179.90
Purchase #4	$33.43	13.123%	$37.817	$37.82	$37.80	$37.80
Purchase #5	$247.35	11.332%	$275.3797	$275.38	$275.40	$275.40
Purchase #6	$225.72	9.650%	$247.502	$247.50	$247.50	$247.50
Purchase #7	$94.85	13.546%	$107.6984	$107.70	$107.70	$107.70
7 purchase totals =	$919.68		$1,009.8709	$1,009.87	$1,009.85	$1,009.90