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	$205.56	9.564%	$225.2198	$225.22	$225.20	$225.20
Purchase #2	$6.71	10.169%	$7.3923	$7.39	$7.40	$7.40
Purchase #3	$144.45	9.189%	$157.7235	$157.72	$157.70	$157.70
Purchase #4	$196.66	4.656%	$205.8165	$205.82	$205.80	$205.80
Purchase #5	$105.48	7.263%	$113.141	$113.14	$113.15	$113.10
Purchase #6	$181.82	4.729%	$190.4183	$190.42	$190.40	$190.40
Purchase #7	$104.77	12.361%	$117.7206	$117.72	$117.70	$117.70
7 purchase totals =	$945.45		$1,017.4320	$1,017.43	$1,017.35	$1,017.30