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	$117.52	9.364%	$128.5246	$128.52	$128.50	$128.50
Purchase #2	$160.74	8.500%	$174.4029	$174.40	$174.40	$174.40
Purchase #3	$38.86	9.701%	$42.6298	$42.63	$42.65	$42.60
Purchase #4	$237.69	3.866%	$246.8791	$246.88	$246.90	$246.90
Purchase #5	$225.61	13.822%	$256.7938	$256.79	$256.80	$256.80
Purchase #6	$140.77	4.486%	$147.0849	$147.08	$147.10	$147.10
Purchase #7	$93.92	6.650%	$100.1657	$100.17	$100.15	$100.20
7 purchase totals =	$1,015.11		$1,096.4808	$1,096.47	$1,096.50	$1,096.50