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	$139.58	3.428%	$144.3648	$144.36	$144.35	$144.40
Purchase #2	$162.30	3.402%	$167.8214	$167.82	$167.80	$167.80
Purchase #3	$38.73	8.134%	$41.8803	$41.88	$41.90	$41.90
Purchase #4	$79.28	13.748%	$90.1794	$90.18	$90.20	$90.20
Purchase #5	$238.38	10.490%	$263.3861	$263.39	$263.40	$263.40
Purchase #6	$244.36	13.160%	$276.5178	$276.52	$276.50	$276.50
Purchase #7	$93.35	4.477%	$97.5293	$97.53	$97.55	$97.50
7 purchase totals =	$995.98		$1,081.6791	$1,081.68	$1,081.70	$1,081.70