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	$199.85	4.766%	$209.3749	$209.37	$209.35	$209.40
Purchase #2	$228.25	8.334%	$247.2724	$247.27	$247.25	$247.30
Purchase #3	$76.81	12.388%	$86.3252	$86.33	$86.35	$86.30
Purchase #4	$72.36	10.855%	$80.2147	$80.21	$80.20	$80.20
Purchase #5	$116.42	9.835%	$127.8699	$127.87	$127.85	$127.90
Purchase #6	$238.42	8.387%	$258.4163	$258.42	$258.40	$258.40
Purchase #7	$232.50	11.638%	$259.5584	$259.56	$259.55	$259.60
7 purchase totals =	$1,164.61		$1,269.0318	$1,269.03	$1,268.95	$1,269.10