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	$138.28	5.370%	$145.7056	$145.71	$145.70	$145.70
Purchase #2	$114.39	8.167%	$123.7322	$123.73	$123.75	$123.70
Purchase #3	$89.87	3.761%	$93.25	$93.25	$93.25	$93.30
Purchase #4	$202.65	6.532%	$215.8871	$215.89	$215.90	$215.90
Purchase #5	$106.77	8.229%	$115.5561	$115.56	$115.55	$115.60
Purchase #6	$157.60	9.330%	$172.3041	$172.30	$172.30	$172.30
Purchase #7	$213.87	9.654%	$234.517	$234.52	$234.50	$234.50
7 purchase totals =	$1,023.43		$1,100.9521	$1,100.96	$1,100.95	$1,101.00