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	$115.34	6.821%	$123.2073	$123.21	$123.20	$123.20
Purchase #2	$194.57	11.812%	$217.5526	$217.55	$217.55	$217.60
Purchase #3	$243.77	13.392%	$276.4157	$276.42	$276.40	$276.40
Purchase #4	$76.78	10.711%	$85.0039	$85.00	$85.00	$85.00
Purchase #5	$55.96	11.658%	$62.4838	$62.48	$62.50	$62.50
Purchase #6	$153.70	7.326%	$164.9601	$164.96	$164.95	$165.00
Purchase #7	$155.84	6.816%	$166.4621	$166.46	$166.45	$166.50
7 purchase totals =	$995.96		$1,096.0855	$1,096.08	$1,096.05	$1,096.20