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	$208.37	6.662%	$222.2516	$222.25	$222.25	$222.30
Purchase #2	$216.28	7.760%	$233.0633	$233.06	$233.05	$233.10
Purchase #3	$197.79	6.649%	$210.9411	$210.94	$210.95	$210.90
Purchase #4	$34.46	12.587%	$38.7975	$38.80	$38.80	$38.80
Purchase #5	$145.38	10.237%	$160.2626	$160.26	$160.25	$160.30
Purchase #6	$48.74	9.371%	$53.3074	$53.31	$53.30	$53.30
Purchase #7	$187.26	9.597%	$205.2313	$205.23	$205.25	$205.20
7 purchase totals =	$1,038.28		$1,123.8548	$1,123.85	$1,123.85	$1,123.90