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	$165.99	4.168%	$172.9085	$172.91	$172.90	$172.90
Purchase #2	$99.80	12.765%	$112.5395	$112.54	$112.55	$112.50
Purchase #3	$196.33	10.255%	$216.4636	$216.46	$216.45	$216.50
Purchase #4	$180.94	3.765%	$187.7524	$187.75	$187.75	$187.80
Purchase #5	$70.44	13.375%	$79.8614	$79.86	$79.85	$79.90
Purchase #6	$14.63	9.188%	$15.9742	$15.97	$15.95	$16.00
Purchase #7	$199.70	13.134%	$225.9286	$225.93	$225.95	$225.90
7 purchase totals =	$927.83		$1,011.4282	$1,011.42	$1,011.40	$1,011.50