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	$154.91	4.770%	$162.2992	$162.30	$162.30	$162.30
Purchase #2	$55.95	5.870%	$59.2343	$59.23	$59.25	$59.20
Purchase #3	$240.39	7.150%	$257.5779	$257.58	$257.60	$257.60
Purchase #4	$92.37	4.801%	$96.8047	$96.80	$96.80	$96.80
Purchase #5	$11.82	10.618%	$13.075	$13.08	$13.10	$13.10
Purchase #6	$209.70	4.126%	$218.3522	$218.35	$218.35	$218.40
Purchase #7	$109.50	13.801%	$124.6121	$124.61	$124.60	$124.60
7 purchase totals =	$874.64		$931.9554	$931.95	$932.00	$932.00