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	$208.51	4.331%	$217.5406	$217.54	$217.55	$217.50
Purchase #2	$209.41	8.863%	$227.97	$227.97	$227.95	$228.00
Purchase #3	$201.80	4.273%	$210.4229	$210.42	$210.40	$210.40
Purchase #4	$243.28	6.744%	$259.6868	$259.69	$259.70	$259.70
Purchase #5	$91.56	8.226%	$99.0917	$99.09	$99.10	$99.10
Purchase #6	$106.71	4.533%	$111.5472	$111.55	$111.55	$111.50
Purchase #7	$40.69	7.231%	$43.6323	$43.63	$43.65	$43.60
7 purchase totals =	$1,101.96		$1,169.8915	$1,169.89	$1,169.90	$1,169.80