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	$121.44	10.651%	$134.3746	$134.37	$134.35	$134.40
Purchase #2	$73.38	4.340%	$76.5647	$76.56	$76.55	$76.60
Purchase #3	$72.53	13.785%	$82.5283	$82.53	$82.55	$82.50
Purchase #4	$84.57	7.408%	$90.8349	$90.83	$90.85	$90.80
Purchase #5	$166.26	11.383%	$185.1854	$185.19	$185.20	$185.20
Purchase #6	$180.61	13.492%	$204.9779	$204.98	$205.00	$205.00
Purchase #7	$160.35	8.841%	$174.5265	$174.53	$174.55	$174.50
7 purchase totals =	$859.14		$948.9923	$948.99	$949.05	$949.00