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	$225.39	11.304%	$250.8681	$250.87	$250.85	$250.90
Purchase #2	$174.63	12.712%	$196.829	$196.83	$196.85	$196.80
Purchase #3	$81.99	9.481%	$89.7635	$89.76	$89.75	$89.80
Purchase #4	$19.81	6.203%	$21.0388	$21.04	$21.05	$21.00
Purchase #5	$198.95	3.818%	$206.5459	$206.55	$206.55	$206.50
Purchase #6	$28.25	10.764%	$31.2908	$31.29	$31.30	$31.30
Purchase #7	$247.45	4.744%	$259.189	$259.19	$259.20	$259.20
7 purchase totals =	$976.47		$1,055.5251	$1,055.53	$1,055.55	$1,055.50