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	$178.28	7.284%	$191.2659	$191.27	$191.25	$191.30
Purchase #2	$213.61	4.324%	$222.8465	$222.85	$222.85	$222.80
Purchase #3	$235.92	13.837%	$268.5643	$268.56	$268.55	$268.60
Purchase #4	$90.90	13.813%	$103.456	$103.46	$103.45	$103.50
Purchase #5	$22.85	4.508%	$23.8801	$23.88	$23.90	$23.90
Purchase #6	$103.60	3.855%	$107.5938	$107.59	$107.60	$107.60
Purchase #7	$112.37	5.229%	$118.2458	$118.25	$118.25	$118.20
7 purchase totals =	$957.53		$1,035.8524	$1,035.86	$1,035.85	$1,035.90