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	$230.48	11.215%	$256.3283	$256.33	$256.35	$256.30
Purchase #2	$202.99	10.790%	$224.8926	$224.89	$224.90	$224.90
Purchase #3	$169.67	7.242%	$181.9575	$181.96	$181.95	$182.00
Purchase #4	$118.55	11.540%	$132.2307	$132.23	$132.25	$132.20
Purchase #5	$122.49	3.504%	$126.782	$126.78	$126.80	$126.80
Purchase #6	$70.49	3.216%	$72.757	$72.76	$72.75	$72.80
Purchase #7	$78.55	12.787%	$88.5942	$88.59	$88.60	$88.60
7 purchase totals =	$993.22		$1,083.5423	$1,083.54	$1,083.60	$1,083.60