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	$199.94	13.706%	$227.3438	$227.34	$227.35	$227.30
Purchase #2	$84.30	11.712%	$94.1732	$94.17	$94.15	$94.20
Purchase #3	$75.96	3.719%	$78.785	$78.79	$78.80	$78.80
Purchase #4	$170.47	6.263%	$181.1465	$181.15	$181.15	$181.10
Purchase #5	$144.47	7.381%	$155.1333	$155.13	$155.15	$155.10
Purchase #6	$112.84	9.409%	$123.4571	$123.46	$123.45	$123.50
Purchase #7	$133.81	7.869%	$144.3395	$144.34	$144.35	$144.30
7 purchase totals =	$921.79		$1,004.3784	$1,004.38	$1,004.40	$1,004.30