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	$71.82	3.783%	$74.537	$74.54	$74.55	$74.50
Purchase #2	$18.35	9.260%	$20.0492	$20.05	$20.05	$20.00
Purchase #3	$241.53	13.216%	$273.4506	$273.45	$273.45	$273.50
Purchase #4	$174.29	13.613%	$198.0161	$198.02	$198.00	$198.00
Purchase #5	$66.37	6.732%	$70.838	$70.84	$70.85	$70.80
Purchase #6	$137.58	6.687%	$146.78	$146.78	$146.80	$146.80
Purchase #7	$29.52	6.113%	$31.3246	$31.32	$31.30	$31.30
7 purchase totals =	$739.46		$814.9955	$815.00	$815.00	$814.90