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	$105.58	7.771%	$113.7846	$113.78	$113.80	$113.80
Purchase #2	$88.86	7.318%	$95.3628	$95.36	$95.35	$95.40
Purchase #3	$246.31	9.292%	$269.1971	$269.20	$269.20	$269.20
Purchase #4	$160.80	13.389%	$182.3295	$182.33	$182.35	$182.30
Purchase #5	$80.80	11.318%	$89.9449	$89.94	$89.95	$89.90
Purchase #6	$162.54	10.239%	$179.1825	$179.18	$179.20	$179.20
Purchase #7	$131.30	8.175%	$142.0338	$142.03	$142.05	$142.00
7 purchase totals =	$976.19		$1,071.8352	$1,071.82	$1,071.90	$1,071.80