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	$239.54	12.503%	$269.4897	$269.49	$269.50	$269.50
Purchase #2	$193.44	8.798%	$210.4589	$210.46	$210.45	$210.50
Purchase #3	$106.32	9.580%	$116.5055	$116.51	$116.50	$116.50
Purchase #4	$30.61	6.516%	$32.6045	$32.60	$32.60	$32.60
Purchase #5	$195.60	13.107%	$221.2373	$221.24	$221.25	$221.20
Purchase #6	$199.34	11.136%	$221.5385	$221.54	$221.55	$221.50
Purchase #7	$227.59	6.678%	$242.7885	$242.79	$242.80	$242.80
7 purchase totals =	$1,192.44		$1,314.6229	$1,314.63	$1,314.65	$1,314.60