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	$198.52	5.854%	$210.1414	$210.14	$210.15	$210.10
Purchase #2	$238.64	12.775%	$269.1263	$269.13	$269.15	$269.10
Purchase #3	$217.52	9.868%	$238.9849	$238.98	$239.00	$239.00
Purchase #4	$81.40	11.668%	$90.8978	$90.90	$90.90	$90.90
Purchase #5	$194.83	12.448%	$219.0824	$219.08	$219.10	$219.10
Purchase #6	$154.70	13.647%	$175.8119	$175.81	$175.80	$175.80
Purchase #7	$65.80	8.435%	$71.3502	$71.35	$71.35	$71.40
7 purchase totals =	$1,151.41		$1,275.3949	$1,275.39	$1,275.45	$1,275.40