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	$93.59	3.779%	$97.1268	$97.13	$97.15	$97.10
Purchase #2	$213.53	11.720%	$238.5557	$238.56	$238.55	$238.60
Purchase #3	$147.40	3.527%	$152.5988	$152.60	$152.60	$152.60
Purchase #4	$229.91	11.606%	$256.5934	$256.59	$256.60	$256.60
Purchase #5	$250.71	3.500%	$259.4849	$259.48	$259.50	$259.50
Purchase #6	$102.48	11.243%	$114.0018	$114.00	$114.00	$114.00
Purchase #7	$164.81	10.280%	$181.7525	$181.75	$181.75	$181.80
7 purchase totals =	$1,202.43		$1,300.1139	$1,300.11	$1,300.15	$1,300.20